I don't run tvheadend on OpenElec, so I'm not 100% how it works. However, if the file is there and readable (which it appears to be) but not showing in the log, then I'd look towards:
1. The log file not being there (e.g. do you have a very short retention period set in the web interface?), or
2. The log file being there but not readable (which shouldn't be the case since OE runs everything under root)
The problem is that I can't tell you where the log files are...! On Ubuntu/debian, they're in /home/hts/.hts/tvheadend/dvr/log. Depending on version, you should see either a list of numbered files or UUID-identified files, each of which contains a record of an upcoming or complete recording. Check that there's one for the missing recording (just grep for "Game\ of\ Thrones" and then explore any files that match).
The fact you say "some of my recordings" makes me pause; if it was "all of them" then I'd put money on the retention period, but check that anyway: web interface, Configuration -> Recording -> DVR Profiles -> DVR Log Retention Time. It may be that you have multiple profiles, and one has a retention time of, say, 0 while another has a larger number, so only the recordings from the first of these disappear, while recordings made with the second still show.