There have been much approved applicants who didn't get the Letter of Introduction/Correspondence letter and was still able to travel without been confronted with any rigid questions or interrogatory suspiciousness, The CBSA already knows this "I think" as if you are to present one then they will know you got it and if you can't then they will also assume you are one of the unfortunate
Every approved applicants has their names already uploaded to the CBSA computer database for any verification and in "my own opinion," the letter is just for mere formal formalities in issuing a study permit at the airport to every approves applicants
If you can't find this letter uploaded to your gckey online account before your departure time, go and board and take along other proof that shows your intention of wanting to travel to Canada
I repeat, many approved applicants has traveled without a LOI/CL without any restrictions, just be reasonable and bold enough to explain when asked and keep mute when not asked.
Good luck!