I wouldn’t of thought it was a thieving toerag they would have stolen the bike and left the chainring bolts, seriously I’ve never had the bolts come loose
I have had 4 out of 5 chainring bolts come loose (chainrings fitted myself) - and realised this 100km in to a 200+km cycle. Quite difficult to tighten with the tools I had. As well as my hex key I needed a wide bladed screwdriver - I managed to borrow a crowbar which allowed me to tighten them sufficiently to complete the ride.
So I suggest that the OP's bolts have just sequentially come loose and fallen out.
If a rider looks down at their chainset (eg after a shift), if one of the chainrings is 'meandering', stop and check the bolts DAMHIKT.
Remedial action: Procure set of 5 bolts; remove and clean chainrings and cranks; refit rings using medium locktite on the bolt threads.