I used the "Edit In -> Merge to HDR Pro in Photoshop" to open and merge 3 shots from LR in CS5. I then saved the resulting HDR as a tif and now I am trying to import it back into LR so it will be in stored in the same the library folder as the original 3 shots. When I try to Import it and path to where I saved it on the file system I can't select the tif. It says the file is already imported.
So I went to "File -> Find" and tried to find the file with the HDR name I gave it and it cannot find it.
From within Lightroom, select the folder (or the parent folder) from the left hand library view and right click on it and select synchronize or re-sync. It will then find the file and re-import it into your library.
I think Howard is right. The trouble is that you are not seeing it in Lr where you expected to see it. Check your file sort order in case it is separating TIFF files from your raw files.
In Ps, I think you just go File Save and it automatically goes to Lr. If you go File SaveAs and give it another name then it may not automatically go back to Lr.
I'm not sure whether it necessarily renames the newly created tiff file or gives it the same name as one of the raw files but with a different extension. Have you told Lr to treat raw and tiff files as one ? Or rather, have you told it not to ? Once they are paired up it is impossible to separate them except by deleting one from outside Lr, and usually you'll only see the raw file within Lr. That may account for the "lost" tiff file unless Ps added some extra characters to the filename (such as HDR) to make it unique in Lr.