No worries. I understand. My imagination thinks that when it comes to volunteers, they can't be too choosy when and how long you show up for. I would think archeologists are chronically short handed for digs etc., so if it were me, I think I'd welcome any volunteers. It's just a matter of finding those circles.
Believe it or not, I used to offer working for free "to get my foot in the door" and was always paid. I think they liked the idea that I showed greater interest than they're used to (most who don't want to work period).
The great thing about volunteering is you're the one in control.
Just throwing some ideas out there...