Well, this is a new first for me. In all the hundreds of data recovery cases I've handled, I've yet to see a single BTRFS formatted drive show up for recovery....until today.
It threw me for a loop at first. The drive had bad sectors at the beginning so I couldn't read the MBR to see the partitioning structure, and all my scans were finding files with no filesystem.
Fortunately, it should be an easy enough recovery now that I know what I'm dealing with.