The cancelled check goes back to the person who wrote it, not the person who cashed it.
If the bank gave the check to the woman, and if Walker actually wrote such a check, he's got a very sound basis for a lawsuit against that bank.
The problem is that we've not seen such a check. Dragonlady insists that the woman provided the check. To whom? No one seems to be able to say, with any degree of certainty, that such a check exists. If it does exist, the time to present it would've been when she presented the greeting card. At this point, even producing the check would be suspect, simply because it's pretty simple to draw up a picture of a copy of a check...