something I never knew about my house

I have gone through the inspection and inspection response process and among other repairs I agreed to the buyers' request to make sure that the heat/AC vent in the hall bathroom is working. Evidently when the inspector checked there was no air coming out. Well, the requisite HVAC licensed repairman came today and checked it out and discovered that, while there is a vent cover in the bathroom, it leads to nothing but a capped duct pipe.  It has evidently been that way since the house was built. The repairman said typically there isn't a vent in an interior bathroom so he doesn't know why this was ever installed.  To actually make it a working vent would involve tearing out a big chunk of the basement ceiling. Needless to say I do not want to do that. After I explained the situation to the buyers (through our agents of course) they agreed that we could forget about the bathroom vent repair. Of course the fact that (also today) their agent came to mine asking that the closing date be delayed a month due to their financing process, made it easier for them to see my point of view on this.  So now we are closing on Sept. 30.Who knows what mysteries might unfold in the meantime.