OP asked in trade for an non specified alchemist to make one bar with the mats for one.
No problem here with said alchemist keeping any that procced.
If the OP asked in trade for a transmute specced alchemist it would be different story. If you specify you want a transmute spec alchemist it's pretty damn clear what you are after.
From the sounds of things,the OP either never agreed that he should recieve any procs from the mats he provided, or he had no idea the alchemist he found in trade was transmute spec. In either case, no agreement was reached on what do to do with the procs.
The OP staked no claim to the procs, therefore they are the sole property of the alchemist.