I think thread merges are, generally, a GOOD idea, if done prudently. However, they can be tricky.

As has already been mentioned by others, there are several ways in which the OP can find his/her post(s) within the merged thread using the Search function. One way is to use the "search this thread" feature and fill in the username in the appropriate box. I've used this, for example, to find my own posts within a lengthy thread.

I hardly think a blanket command to "please stop merging threads" is warranted just because of a particular difficulty with a particular thread (and lack of knowledge about how to find one's own posts).