To clarify a bit more, this question: Were the signatures valid?

IMO and understanding sometimes signatures are not valid. Just because there is signature doesn't make it valid.

And one more thought/observation from my experience. I was at the bank making a deposit. The guy in front of me gave the teller 3 100 dollar bills, well he thougt they were 100 dollar bills. The teller tells him they are counterfit. She holds them up and shows him the proof with phony serial numbers that are on a list in front of her. The guy was upset. Wanted them back. Wanted to see for himself. She said no and he tried to reach over the counter. She told him she was sorry but they now belonged to the government. He protested that he would be out 300 dollars. And he was. He told her he took them in good faith from his customer. He still didn't get the 300 dollars back. He managed a hotel and the travelers who paid him were gone. This was about 15-20 years ago. Most hotels now require a charge card deposit on file. The barn doors are now closed, but not before he lost his 3 horses.