Most likely to be nothing more than the previous owner needed to swap a tyre, especially if one is generally more worn than the other. One of my cars is like this due to a cut tyre but if I didn't know it would be confusing
But if the car still sits unevenly on a flat floor I'd be suspicious and I would try to find a place that could do a full 4 wheel geometry check with a corner weight. The only guy I know is quite a long way from you and has gone radio silent recently so I can't help there
Is the corner that squeaks the same one the more worn tire came off and is it the same one that you originally said was sitting lower..
A tip, when talking about cars don't use left and right. Use driver (offside) or passenger (nearside). Left/right swaps sides depending on where you're looking from