Last weekend I opened 2♥, alerted and correctly explained as "♠, either a weak two or a strong two-suiter". LHO places the Pass card on the table. My partner thinks for a while, then also puts the Pass card on the table. RHO quickly says "Pass" and partner almost at the same time "oh, sorry". Since there is still no Pass card to my right, I claim that RHO has not yet made his bid and partner can still correct to the 2♠ that he wanted to bid anyway.
How would you rule?
Plus... it's free!