While in Photoshop, you always need to do a "save", never a "save as", else Lightroom will not know what happened to the new file.
Depending on the sort order of the images when in LR, the new image may or may not be placed near the original file(s) in the grid or film strip.
I have this same problem. I go from LR to PS via 'Edit in". When finished in PS I use Save/Close (Cmd W). The file goes through a save but when I return to LR it is not visible.
The frustrating thing is that this has been an intermittent issue for the last few months. Sometimes everything works smoothly with the return ending up visible in LR, and sometimes the condition described above.
I have read several of the comment sets and none seem to address this situation exactly.