I would have banked my 26 grand and went back online to see it that doofus had anything else good for sale !
You DON"T take that kind of cash and "Drop" it in your bank account. The bank HAS to report it to the "Feds",then the nightmare begins. The IRS,and the DEA will come knocking on your door. Put the money in a coffee can and stash it your freezer.
About 6yrs ago I sold a collector car (Shelby Mustang) for Alot of money. I was offered cash I said no give me a certified check.(I knew the buyer's reputation and knew the check would be good). I told my CPA about it and he said never take that kind of cash, Too much grief.