Maybe 10 minutes later I could pick up enough landmarks to be really positive about my location, drew a line and got back with the program.
The problem with getting lost and then finding the landmarks you were looking for is that you may have found a second similar looking set of landmarks.
THAT is the danger in dead reckoning. If you do make a big clanger (like totally forgetting to start the stopwatch and not realising until 10-20 mins later, or flying 080 instead of 180) then there is a high probability of finding a false positive on the ground.
The key in this is to pick waypoints which look as bizzare/unusual (in their area) as possible, so the risk of the above mistake is minimised, but it is still easily done especially when flying over feature-rich terrain.
The wonderful thing about radio navigation (GPS, VOR/DME etc) is that you get a
continuous guidance along your track, so if you get distracted for 5 mins, nothing major is going to happen.
To get anything like an equivalent continuous guidance using dear reckoning, you need to be constantly matching the map to the terrain below but this is not always possible, due to occassional lack of clear features.