All is behaving as designed.
When a flash memory card goes into a camcorder (or still image capture device like a point and shoot or dSLR), the manual says step 1 is to format the card in the camcorder. The camcorder's embedded "operating system" sets up the folder directories for stills, moving images, etc... and a proprietary database index that keeps track of the media file numbering system (its version of the file names), where the files are located on the flash memory media and a bunch of other information that only the camcorder can use within its "operating system". When you renamed the file, the proprietary index system lost track of it. If you rename the video file back to what it was, then the index file might recognize it and all will be back. It is possible that the proprietary file system will not recognize the file even if you return to the original name because of the various date/time stamps you mentioned that also are modified by the computer's operating system.
The camcorder is not a "personal media player" - it is designed to capture and store - and playback what it captured and stored. Changing the name of the file as you did means you changed what the camcorder captured and stored.
Link to the manual
Initialize the memory card in the camcorder: Page 31 and 32.
Some of the data tracked by the index file: Page 40 (Select scenes by recording date), Page 41 (Selecting the playback starting point from the movie timeline), 42 ("Index screen")... there are other references to datacode and accessing files...
Page 77: "IMPORTANT: Do not access, change or delete folders and files in the camcorder directly from the computer as this may result in permanent data loss."