They could easily see your partition table(and it will hint that it's ZFS). But they wouldn't be able to gleam much from your drive without serious forensic analysis. If you had compression enabled that's a hindrance, since it was it's own vdev, that's a hindrance, the different block sizes also are a hindrance. If you have files in plain-text and compression wasn't used they may be able to read it. But when it comes to getting large quantities of data it'll be very limited in what they can actually get off the drive.
I've actually decided to try recover the data. I have a lot of irrecoverable stuff on there, and even the recoverable stuff will take months or years to build back up. If I take it to a forensic analyst, what are the possible outcomes? I mean, what are the possibilities that would get my zfs volume back? Physical disk recovery? I assume partial data recovery won't be of any use to me. Basically I want to know that if he calls me up and tells me what he can do, I'll be able to tell him yes or no.