I recently gave 3 lessons to a guy on his shiny new 12m Drifter and all I can say is has been horrible. The kite will not relaunch in lighter winds, and I tried holding in various amounts of rear line,, kite depowered, kite powered, sheeted in/out and it would not get up on a wingtip at all. I figured I could do a c-kite relaunch with it- as soon as it started to go onto its back, it lifted off the water and inverted the lines.
It will relaunch in higher winds, but you have to pull the rear line hard and hold it for a while to get it to turn over. I can't even imagine dropping that kite in the waves and trying to relaunch.
Not sure what kite you tried, but it was not a 12m Drifter. The Drifter does not come in a 12m. It comes 5.5, 7, 9, 11 and in 2013 they added a 13m. Maybe it was a 2012 Switchblade? If so the larger SBs prior to 2013 are known to be very hard to relaunch in light winds, and I would agree with you. However, the 2013 SBs are much much easier to relaunch because of the squared off wing tips. There may be faults with the Drifter as a flatwater kite, but relaunch is not a problem. I cannot comment on the 13m but the 9m and 11m relaunch immediately, and I have put them down in the surf many times. I have never heard anyone say there is difficulty in relaunch. If you had problems then either they were flying it on a non Cabrihna bar that did not match well, or the wind was just way to light. Although I am assuming the kite was not a Drifter, calling a wave specific kite "crap" because you could not launch it in light winds seems a little silly. Like I said, I cannot comment on the 13m, and maybe it was a 13m and maybe the 13s are far more difficult to relaunch. But still it is not meant to be a lightwind flatwater kite, and few people fly large kites underpowered in the ocean.
The Drifter is a great kite for what it is designed to do. If in fact this was a Drifter which I doubt, the problem with your local shop is not that they sold your student a bad kite. The problem is that they sold them a wave kite in a place without any waves and little wind. There are a lot of light wind flatwater kites out there and you are absolutely correct that the Drifter is not one of them.