Fact needs to be acknowledged that HIS gun-time was 2:13 not 2:18.
Chip-time is not accepted because everyone is meant to start together and it is your own fault if you're not across the start line quickly. Gun-time refers to when your race starts. His race started 5 minutes after the elites and therefore his gun time was 2:13.
I think he should be paid but is definitely not "4th" because the others had no way to react to him (though 2:13 from hte masses is clearly more impressive!) but in this situation it seems clear that there were 2 races and he won the "second" race. Of course the question now arises that should Chicago make it clear that its prize money is only available to a select few who are in the invited start.
Much more embarrassing than this situation would be if someone from the masses ended up running faster than the winning time -serious problems if that ever happened. In this case thankfully the prize money is relatively small compared to the race size.