There are two simple, relevant facts here.
1) Systems do not disappear. Period.
2) If you can get to a system you can get back from it. It may require some fuel management, jumping on fumes, etc, but if you got there you can follow the reverse route back.
Try to download EDDiscovery, run it and have it pull your travel logs. Then follow your way back.
+1 vrep Cmdr - excellent advice.... EDDiscovery or Captains Log, both can import logs and allow you to trace back. I had to do this myself when I was 65klys out...
Recommend marking systems use fume jump to/from so you remember to manage fuel loads on the way back..
Cmdr A