It is not illegal for them to bill .
Before he went to collections , which should have talked to your billing department. Normally, in case of emergency your insurance company must pay more than they would for "out of network" normally. Second, did you have medical insurance car ? Should compensate for any deficit that exists between the amount your insurer will not pick them up.
If anyone was at fault, your insurance should pay for things that are not covered .
You CAN NOT be " in the collections of " the way most people mean . A lot of hospitals use a collection agency early in the billing, but you see it says to pay the hospital or contact them for information / disputes. That is not the regular collections where it is cents dollar debt that is sold.