A FRU is a "flat rate unit", equal to 1/8 hour of warranty time.
As for a diagnostic report, I don't really know what you are expecting. It sounds to me like your dealer gave you some false expectations. The only "report" that I could think of would be a print out from their battery tester giving you the stats on the battery that was in the car. Also, they could possibly have a print out showing that the fault memory in the car's computer was clear. Other than that, I have no clue what they could possibly have meant.