Forgot to refill transmission fluid

Took my 2005 Honda Odyssey into the dealer about 10 days for a 15,000 mile service. I later noticed some trouble in accelerating, but I didn't have experience with transmission trouble so I didn't recognize it and plain didn't expect any serious problems with an almost-new car. Sometimes it seemed to drive OK.

Yesterday, the van broke down (would turn over but refused to engage) and had to be towed into the dealer. Finally I suspected that the fluids had not been properly replaced during the last service. My husband and I checked the transmission fluid and sure enough it was bone dry. We checked and found no signs of leaking. The only explanation I can figure is that after the mechanic drained the fluid, he forgot to replace it.

I made sure that the service manager went with me to the van and confirmed that there was no fluid and no obvious signs of any leaks. He apologized and set me up with a loaner car, but seems to be taking some time to examine the van's transmission. I'm worried that he is stalling and trying to do the very least possible.

My gut tells me to insist upon a new transmission. My husband says we should only expect to get the problem fixed, but I am worried about hidden damage and trouble down the road. What would you advise? Any ideas on how to make sure the service manager does us right in this situation?