I was working on a high-profile race a couple of years ago where something similar happened. Problem was, no-one could work out if it was towing or if the rider had taken a lap out then jumped in somewhere near the front group but out of sight of cameras/Commissaires.
Bottom line was that no-one had seen anything untoward – we knew something was up just from the timings of the groups on the road but with no absolute proof the result had to stand.
Teams are always very quick to complain about other riders, other cars etc getting what they perceive to be an unfair advantage while at the same time trying any underhand tactic they can get away with too.
At the moment, Commissaires don’t have the power to act on power/Strava data, especially post-event. A Commissaire’s power ends once the race has been concluded except in cases of giving out fines collected during the actual race. They aren’t permitted to go back to a race from yesterday, last week etc and re-jig the results just cos a rider was caught cheating.
The UCI might still have the power to act on it but it would require a lot more evidence than this (although you’ve got to admit, it’s a weird coincidence that he’s deleted his Strava file…)
With the march of technology, it would be possible (although very time-consuming) to interrogate everyone’s data afterwards but it would turn the sport into nothing more than number crunching and you end up with armchair experts tearing everything to shreds (much the same way they did when Froome released all his power data).