In Germany they do search for you if you fail to close within 30 minutes of the filed arrival time. Happened to me several times. However, nobody files a plan these days unless they're crossing a border that requires a flight plan. Germany does not require VFR flight plans when coming from abroad or when going abroad so you only need it if the other country requires it. For France it's mandatory and when landing at a non towered airstrip in France, I always call up the French AIS and close the plan.
The "best" experience I had so far was on a VFR trip from Poland to Germany via the Czech Republic. Due to weather, I couldn't cross the mountains between the Czech Republic and Germany and had to turn south to Austria to follow the danube. All was done with FIS from the start to arrival but my flight plan was never forwarded to Austria so all the time I was flying through Austria, I was missing. The extra time required made the German AIS initiate the uncertainty phase and I just arrived in time in German airspace to avoid a SAR mission. My attempts to find a passage through the obscured mountains with lots of 360s on the radar track probably didn't give them much confidence when they started investigating my whereabouts. Never seen them to happy to hear me on the radio
