I remember a time when you could buy jeans, even on the tight side, and put them through hell - they were made of ‘tougher stuff’, that fabric from Nimes, and were stitched with what would better be described as cord not thread - thick thread at least. Only a significant lose off a skateboard onto bitumen or off a dirt-bike while mustering stock was enough to exceed the limit, and even then … or worn out after a long time, over six months of regular wear. As long as they aren’t ridiculously tight.
Three months - no. Even the cheap and nasty jeans Target sells should last six months+ and a couple of years back I returned a pair to them with no complaint (and no replacement - they were rubbish).
There might be mitigating factors, if they were distressed, bleached for style, or some other fashion thing it might detract from durability, but your post doesn’t suggest they had any ‘special fashion features’
I’d go back and have a chat with the people who sold them - you might be surprised.