Your magic numbers don't seem to guarantee consistency either, multiple faulty exchanges and the file could be gone forever: maybe random numbers happened to be the same, or the sum of substractions during faulty exchanges got to 0, or there was an overflow, etc.

Distributed algorithms are not easy, but for this case there are proven solutions, look up how Riak deletes records for example, with "tombstones" and "reaping". Basically you have to think in terms of CRDTs and have a log of operations, a versioning scheme, a synchronization, etc., all of which help you to make sure that no operation is applied twice anywhere and that in case of faulty communications nodes can synchronize and apply missing operations. This gives you consistency, eventually, and a reliable way to know when files can be physically deleted. Or, you know, just use Riak.