Without the card in hand I can't say for certain, but I too think it unlikely to find an original 1961 card in top condition in a random pack of assorted cards sold in the team shop. Those packs tend to be commons and over-produced 1990's era cards. To find an authentic 1961 card in one of those packs seems very unlikely to me, and for that card to be a legitimate star on top of it? Probably not gonna happen.
There were reprints of that card made in 2011 (https://www.tcdb.com/ViewCard.cfm/sid/56686/cid/1898667/2011-Topps---60-Years-of-Topps-Original-Back-290-Stan-Musial) as well as some buybacks in 2003/4.
If the card isn't an original, I would tend to label it a forgery rather than a reprint though. True reprints are labeled as such or at least have updated copyright information clearly indicating it was produced later than the original card (the 2011 reprint, for example, is clearly labeled "Topps Reprint" with a 2011 copyright date on the back of the card). Simply printing a scanned/photographed copy of the original card without clearly marking it as non-original seems, to me, to be unethical.
Hey, hopefully you got really lucky and pulled a great card (even with grades of 4-5 that card is selling in neighborhood of $50), but if I had to bet, my money would be against it.