You could take an oil sample to see if any glycol is in it. Of course if it is just being caused by condensation with short trips it will not be in the oil.
We experience quite a few cars that are only short distance driven for years perhaps before purchase. Not unusual for them to drop their oil level quickly on the first hot run of some distance. In fact a good reason to change the oil as soon as you get a car if you do not know the last time the oil was changed.
A rapid drop of one or even two quarts is not unknown. All the accumulated moisture and contaminates with a lower boil point than oil get boiled off. Now the real question is it wise to buy a car that experiences this? We have lucked out so far but may not always. Normal oil change intervals are not good enough on cars that have only very short trips. Ownership of a car should mean at least one extended run a week in my opinion. I find it amazing the engines seem to tollerate this short distance treatment as well as they do. You have to make sure of course the dealer has not just changed the oil before pulling an oil sample. Or the test may not be valid. Might help answer your question though.
edit: I just finished reading the refference post to this problem on the 112 engine type. Pretty bad for what these cars cost new in my opinion. You have a different engine without it being a chronic problem like the 112s as far as I know. Unless created by bad habit owner use senarios or something like a head gasket as you mentioned. Easy enough for you to find out though.