Your LFS is mistaken. Rhinos are actually fairly far down on the list in terms of toxicity...add to that, the fact that they have long, thin, flexible dorsal spines which make it fairly hard to get poked.
Neither Renee nor I have ever been stung by any of our venomous fish (not even during the move).
That being said, our Eschmeyeri decided I was too close while cleaning the tank and it gave me a warning not to get any closer.