... I think it may have been a brute-force attack.
Unlikely unless you're sloppy.
To prove the point, 10 bitcoin for each pass for any of these unsalted MD5s:
824cfad07c88261afb4dd3285627887a
73550477b12849b2a4dcd3b0db187415
3e567bcbb2aa5c28c47012b857bf6e48
3709fb6b0e1c0b26ff22a19ae92fd080
9133c451dd761d29943dcc653252e2fa
ff111d6144367b4abd99aa4321b0a618
8602188ef5a05a13afc59c51b395426c
da842aa7c84236d17a04098fa1273f2d
Have fun! ;P
EDIT: alphanumeric only. I'll pay legitimate finds or my name is mud!
Challenge accepted.