Deleted/disjoint waterways - how to find?

Is there a way of finding waterways which have been deleted during the redaction process? (usually waterway=stream)

I have been checking waterways using OSMi, and have found a lot of them deleted by the redaction bot during the license change in 2012. Now, this means that the water network is disjointed in the map; unlike highways, this has gone unnoticed for so long that I can't find any post-redaction QA tools.

An example to clarify:

• 2012: situation out in the terrain: Stream A flows into Stream B; Stream B flows into River C.
• situation in OSM: everything mapped, but the mapper of Stream B did not agree with the new license.

• the redaction bot cometh, and deletes Stream B (this is expected behavior, and I'm not asking about this)

• 2014: in the terrain, Stream A still flows into Stream B, which flows into River C

• in the map, Stream A now does not flow into anything, it just ends; it is not connected in any way with River C
• I want to find these situations and resurvey, so that OSM mirrors reality again :)
• This seems to be a very common occurence around [50N,15E], so I'm looking for something more robust than "just look at the map and see if it seems weird"
• (Some sort of graph traversal comes to mind?)