Hand is approximate, but it is a maximum 15-17 NT hand with good hearts and a nothing doubleton in a side suit (i.e. a hand that wants to play 4♥ across an invitational hand with heart support).
Initially, I see my partner's rebid (incorrectly) as 3H.
I pull the 4♥ card from the bidding box and have it in my hand above the table, facing me. At this point, I am uncertain whether partner can see what card I pulled, but I'm sure at least one opponent can. I now notice that partners bid is 3N not 3♥.
This is not a mechanical error as I fully intended to bid 4♥ when I pulled the card.
Not being sure what to do (and a bit flustered), I completed the bid and went down one in 4♥ across from a doubleton heart holding when 3N made at the other table.
My question is what options if any I had here (a) after noticing my mistake but before placing the bid on the table, and (b) after placing the bid on the table?