The recording log is just that ... a log of recordings made with the status of that recording. So you can not remove entries from the recording log. They are removed after the number of days as mentioned in the DVR configuration page (DVR Log retention time (days))
It also contains a link to the file location that was created when the recording was made and a status of that recording. If that file is still there, you can "play" it directly from that location via the webgui. If it is no longer there, then that link does not work.
Removing a file from the filesystem does not remove it from the recording log (and also the otherway around, when a recording log entry is remove, it does not remove the recording)
A status of missed means that you had a recording scheduled, but because there were no tuners available, or the machine was not running, that recording was not made.
Most of the metadata that was present when the recording was made is available in the recorded MKV file. This is one of the main reasons to select mkv as the recording container for tvheadend. You can view this data using standard tools that can work on mkv files. (for example mkvinfo)
Also keep in mind that tvheadend never removes recordings by it self. If you run out of storage, then tvheadend will just stop recording until some more storage space is made available.
Hein.