In NV casinos there is always one last rule on the list of posted rules.
"Floorman's decision is final."

My guess is two different floormen would call this one differently.

Cards released face down in a forward motion "may" be ruled dead.
Cards released forwardly face up are not dead.
Face up in the muck "may" be dead. the key word here is "MAY."
Face down in the muck more than likely dead.
That said I have seen hands pulled from the muck to be a winner. There can be cases where it is the right call.

I would ask the two players to split the pot so I did not have to make the decision.

If forced to make the decision, seat 3, would not like it.

In NV seat 3 would have the option of calling NV gaming to protest my decision. I do not have to call them because it is under $500.

NV gaming could go either way. They might rule seat 3 should get the pot and the house has to pay it.

IMO, spliting the pot was the way to go.