Originally Posted by
etch5895
You may not have gotten a stamp but the immigration officer certainly scanned your passport when you entered. There is definitely a record of you entering so I would be surprised if you encountered any difficulties leaving. That said, it is sloppy for them to not stamp your passport. Did you enter Schengen in Frankfurt?
There is no unified electronic system for recording arrivals and departures from Schengen so depending on which country one departs from it is entirely possible that there will be no record of arrival if the entry stamp was overlooked. That being said, it is unlikely to cause any difficulties at exit as it happens all the time (FCO is notorious for failing to stamp).