Okay, Nathan, you are asking a difficult thing.
My memory doesn't bring to mind if you already stated so but I am ASSUMING this was standard pipe, not some exotic material. I am ASSUMING you have informed us correctly and that pre-heat, if required, was applied per a wps. I am ASSUMING you were using compliant electrodes for welding. As you can see, we, as not present on site opinion givers offering free opinions (which are like armpits, everyone has two and they both stink) are hindered by many unknowns.
Also consider, did this moisture come into contact during welding, immediately after welding over this area, a minute or two after welding, or 5 minutes after welding. I don't remember this being stated precisely. Add to this, did this inspector see the drops hit or just see evidence of moisture on the weld sometime later? If you could still see evidence of moisture but did not see it come into contact while also witnessing the welding while in progress then he is assuming a lot as well. Difficult to justify a conclusion based upon so much speculation and assumption.
Now, though, as to your question about our 'opinion'... More than likely, it did not bother the quality of the steel pipe and/or weld metal. It does not 'sound' like there was enough moisture to have truly effected the hydrogen content nor the cooling rate of the pipe (my statement earlier about sweating on our work while welding and if this practice is supported we would be cutting out a lot of welds). But, that is ASSUMING a lot of things and I am not the customer's representative. I would agree with some of the others, it isn't a matter of code and/or quality of product, it is a matter of authority and showing that he gets what he wants right or wrong. And he is going to make sure you are soundly reprimanded for this 'little' mistake.
**SPECIAL NOTE: NOTICE ALL THE 'DISCLAIMERS'!! I ACCEPT NO LIABILITY NOR RESPONSIBILITY FOR ANY ACTION OR STATEMENT MADE BY OTHERS BASED UPON MY 'OPINION'!
Disclaimers are things like: 'more than likely'; 'does not sound like'; 'assuming'; 'our opinion'; etc.
Have a Great Day, Brent