I contacted the STN police station and was told there was no way I could have the offending item back.
I was told that "BAA security people hand over confiscated stuff to us and we put it all in a big bin which is taken to headquarters at Chelmsford for disposal. There is so much that it would be difficult to find your multi tool, sorry sir."
Interestingly, I was told that I should have been given a confiscation notice by the BAA secuirty people.
Wonder where the multi tool is now?
Must try to get another one. Seem to be many, many genuine Leathermen for sale on the E-Bay auction site on the net.