Apparently my lab received them and return posted them to me on March 4, over a month ago. They said they can try to make a claim to the post office which might get me some money back, but can't get my images back!
The films included the Rollei shots from San Francisco and also the films I finally found from my trip to Zaragoza over Christmas. These shots were quite valuable to me and it was a double disappointment to have finally found the films only to lose them in the post.
The lab assured me that things only get lost in the post on extremely rare occasions and they think it will turn up sooner or later. Who knows....
If anybody out there received a package in error please send it back to me!