Legal Question in Credit and Debt Law in Pennsylvania

Not usually.

Did you happen to make a copy of the check that you sent and do you have a copy of the check that was presented to your bank? What did they write in the memo line that causes you concern?

Information in the memo line does not affect the negotiability of the check - I use it as a reminder of what I paid for on those rare occasions when I write a check like (or dental visit, eyeglasses, the veternarian for my pets etc. However, if the line was blank and someone wrote the words "loan payment" in the line that might have repercussions.

I would have to see what was written to know for sure. If someone asserted a claim against you, you would have the burden of proving that the check was altered.