The deal was between Campaign manager and the project owner, none of the campaigners owe anything. Have you been paid for the week/weeks you wore the signature. The answer is yes. Case close for campaigners.

If managing a marketing business was so easy, not required risking loss, only profit then I would not have to pay many times several thousands if not five figures already out of my own pocket in several campaigns. I don't think that time many members were too keen to accept a no payment (sometimes a few but it's not even 1% of the total).

What I am saying is: loss, left, profit, whatever it is - it's the deal between two party.
One > The campaign manager
Two > The project owner.

You, me and rest of us owe nothing. We are third party.

Making a written contract like not claiming the money after x days/weeks/years will result xyz can be a good idea though. I have done it with few of my clients but it was more formal like -
If the project end up with bad reputation and communication disconnected for x months then you (project owner) do not owe anything from the escrow fund. It will be use to cover loss of the campaigners and management business.

The answer from them are always yes.