He must have been too late. First, you observe, then you go in when he's not there as you might be able to find the information you're looking for
without confrontation, then you kidnap. Haven't you been to the movies?

Anyways, Cerberus was on step 2, but Cromeline had flown the coop by
then.
Don't worry, we'll find the rings. Cromeline has way underestimated us - he's too sure of his own skills. Overconfidence will be his downfall.