Are there records of passenger ship SS Groote Beer arriving in North America in June 1957? I have the passenger list (from Rotterdam) with my grandfather's destination (Montreal). The arrival seems to be missing from American immigration / ship records

I have searched high and low, but I cannot find any documentation of the arrival of SS Groote Beer or her passengers in North America in June 1957.

My grandfather embarked from Rotterdam aboard SS Groote Beer on June 7, 1957 bound for for Montreal. I have the passenger list indicating these details (from passenger lists of Holland America Line available from Rotterdam City Archives).

The most approximate records of other voyages of Groote Beer to/from North America that I have found (relative to my grandfather's voyage) are located in Rotterdam City archives: 
Record 1: a voyage embarked May 25, 1957 from Montreal, Quebec to Rotterdam, NL
Record 2: a voyage embarked July 12, 1957 from Quebec City to Rotterdam, NL
 
These records are the most approximate to my grandfather's voyage in chronological order:
"Record 1" corresponds to the start of the voyage that immediately preceded my grandfather's embarkation from Rotterdam on June 7, 1957
<record of my grandfather embarking from Rotterdam on Groote Beer on June 7, 1957> (found in Rotterdam City Archives)
<no available records of Groote Beer arriving in Canada or U.S.> (it should be in US/Canadian archives about June 19, 1957)
<no available records of Groote Beer leaving Canada or U.S.> (it should be in US/Canadian archives, and should also date June 19, 1957)
<record of an embarkation from Rotterdam on July 2, 1957> (found in Rotterdam City Archives)
<no available records of Groote Beer arriving in Canada or U.S.> (it should be in US/Canadian archives July 12, 1957)
"Record 2" corresponds to the voyage that immediately followed the scheduled disembarkation in Quebec in July 1957
A simpler way to put it:
Montreal (May 25) >>> Rotterdam (June 7)
Rotterdam (June 7) >>> Montreal (~June 19) (no immigration records for my grandfather or any other passengers aboard SS Groote Beer)
Montreal (June 19) >>> Rotterdam (July 2)
Rotterdam (July 2) >>> Quebec (July 12) (same thing, no immigration records)
Quebec (July 12) >>> Rotterdam (August 5)
So it seems the immigration records of Groote Beer in North America mid-June through mid-July do not exist.
I have found records of other voyages of SS Groote Beer from earlier in the year and also from later in the year that do have immigration records, so I am not sure why they are missing for June/July.
Of interest, I found one post (in a FB group dedicated to SS Groote Beer) by a person who arrived on SS Groote Beer as a child in July 1957, who indicated there was irregular disembarkation that summer. He stated:
"My family sailed on the Groote Beer in 1957 from Rotterdam to a farm field west of Quebec City where we had to disembark via a wooden boardwalk . There was a longshoreman strike in Quebec City so we couldn’t disembark there. We walked across the farm field to a train waiting for us to take us to our destinations.[...] We ended up in Ontario[...]"
So I searched for his family name and found his father on the passenger list from Rotterdam to Quebec on July 2, 1957 (the voyage after my grandfather's voyage).
Then I searched for information on a longshoremen strike in Quebec City in 1957. All I found was the following:
- Newspaper articles referring to an international longshoreman strike (all along the East Coast of Canada & the US) that began in February 1957 and ended in March 1957 (which does not correspond with the mid-summer voyages). So that is confusing.
- The only strike that I found records of in Quebec in the summer of 1957 is the Murdochville Strike, which lasted from March through October (there was some violence and at least one striker was killed, but as far as I can tell it was not directly associated with the ports of Montreal or Quebec City). So that doesn't really add up either.
 
Perhaps there was a longshoremen strike in Quebec that coincided with the arrivals of the Groote Beer in June and July 1957, but I just haven't found records of it yet.
Perhaps something happened to the immigration records?
Or perhaps I just haven't looked in the right place? (most likely)
I have submitted a request to the USCIS Genealogy Program for any information pertaining to my grandfather, so when I receive that information I will try to trace it back to his arrival on SS Groote Beer, and hopefully discover what happened.
If it is of any use, my grandfather's name was Mariano Sancho Manrique.
On the passenger list he was recorded as Manrique-Sancho M.
It is possible, due to differences in naming conventions between Spain and other countries, that his name was recorded as any combination of the above.
This links directly to the page of the passenger list with my grandfather's information. He is on the 6th line from the top.

Please help! Thanks!