Oh, what fun! Wolfus had quite an adventure, didn't he?!
Sounds like you need to get some locking clips. The rule we were given when we first got our BP was "if you can lift it/move it/open it, then the BP can lift it/move it/open it." Going by that rule, our wire spring clips weren't good enough, and neither would plants or rocks or blocks have been good enough. It's truly amazing how strong these creatures are!