"They were reimbursed for the cost of collection, but not the lost revenue."

We have a saying here: you cannot write Off what you did not write On.

There is no Revenue to write off, for tax purposes. Otherwise, what's to prevent you from valuing something at some inflated market rate? Especially in light of their Cash Basis, which means: we didn't lose any realized revenue; we lost Potential revenue.

And since they got reimbursed for their costs, they cannot write off that expense, either, even though they lost the asset and any basis in it.