It wouldn't surprise me if they phoned up airports to verify t/o and landing times once in a while - it would be relatively easy to do and you might hope to catch any substantial percentage of parker hours with only a few calls.
Early on I messed up the way I'd recorded all my times and had to copy out about 40 hours of flying into a new logbook. It was surprisingly difficult to do without making a further mess. The flying school kept a free stock of identical biros so even legitimate hours logged probably looked suspicious!