Low Mouthfeel

At the brewshop tonight someone brought in a beer, it was a nice little pale ale with good flavor but very low mouthfeel. Given the recipe  and his gravities I don't understand why it was so watery. recipe was something like (5 gal) 4 Lbs Munich, 5 Lbs 2 row, 1 Lbs Carapils, 1 Lbs C20. OG 50 something FG 10. he uses us05. Any thoughts on why? He bought some maltodextrin for future batches which should help but I can't figure out what caused the problem.

Could be in the mash schedule;if he used a protien rest ( even accidently) it could have desroyed some essential prtiens.Happened to me recently.( at least i think so).I overshot my acid rest w/faulty thermometer to blame and landed @ 121 deg f.Discovery was post 25 min.after the fact.  :

Based on the information you provided I would have expected a higher ABV and higher OG - for a 5 Gallon batch... so I would agree with the earlier statement that it may have been something with the Mash Schedule or possibly the sparging process.  For a Pale Ale I would mash at between 149-151 and then make sure to get temps to 168 for sparging (either via mash out or batch sparge depending on your process).  For this type of beer I think a single step mash would suffice at 60 minutes.