As if the Cleveland Browns season couldn't get any worse ...
Robert Griffin III's girlfriend claims a valet at FirstEnergy Stadium in Cleveland ransacked the wallets they left in their car during Sunday's game ... and stole all of their cash.
Grete Sadeiko -- who has been publicly dating RG3 since the summer -- said she left her car with a valet in the "players and family garage" to watch the Browns take on the Giants ... and when she returned, the money had been taken out of their wallets.
Grete posted about the alleged incident on Twitter -- and when people began to question why she left their wallets in the car in the first place, she roared back.
"Ain't about why we left wallets in the car we parked in PLAYERS AND FAMILY PARKING GARAGE! I should be able to leave anything I want there."
We've reached out to Cleveland police -- who say they have no record of a report being filed about the incident.
We've also reached out to RG3 and Grete -- so far, no word back.