Another leak question...

Hello all. New to the forum -- and to Eichler ownership. My wife and I purchased a "double gable" Eichler in Thousand Oaks last year and are neck-deep in a renovation. Initial inspections cleared the plumbing and radiant floor system, but a water problem has suddenly appeared now that we're nearing the end of the project (of course this is only happening now that the walls are closed up, kitchen cabinets are in, island built, countertops on, etc).  
 
In any case, after weeks of trying to sort our water issue we have opinions from two plumbers, two leak specialists and one contractor, all of which are different. Though it might prove even more confusing, I'd like some perspective from other Eichler owners if you've any to offer. Apologies for the length of this post, but here's the order of things:
 
1. We found water on the floor of the guest sink area and in the front bedroom, behind the guest sink wall.
 
2. An independent leak detection specialist with lots of fancy equipment spent a half hour  tracking down what he said was a leak in the hot water pipe in the slab running next to the guest toilet.
 
3. A subsequent leak specialist hired by the insurance company found the problem to be a nail in a pipe in the guest sink wall, introduced by a workman -- and why didn't the other guy find this? It took the insurance company's guy two minutes to find and I immediately dismissed the former specialist and his "leak" as bogus.
 
4. The nail hole was patched, but the next day we found two puddles of water in the kitchen: one dead center on the kitchen floor, in front of the sink but with no water anywhere near the sink, and another smaller puddle under the end of the dining room wall where it comes into the kitchen. 
 
5. Re-dispatched, the insurance company's leak guy was mystified by the puddles and eventually concluded they're to do with the radiant floor heating system.
 
6. Now, the insurance company is sending a floor heating specialist.
 
Thing is, when the puddles appeared the heating system was off with no water flowing into it (that we know of). With that system shut down and with the water main on, water appears in the kitchen. Is there any chance it could be from the floor heating system?
 
Could it be the original leak guy really did find a leak (the one by the guest toilet) and that water from that is somehow finding its way back to the kitchen area? Seems ridiculous but I'm still wondering if that guy really did find something.
 
Over six months of renovating, there were no other leaks apparent anywhere and no water in the kitchen where the puddles are now appearing.
 
Any thoughts -- or recommendations for Thousand Oaks-area plumbers who know Eichlers?  Thanks for any comments.