To answer your question, no this isn't a big deal and it shouldn't discourage you. LDs can be a bit random so you can't put too much weight on one particular night, either positive or negative.

For the sake of curiosity though, it's possible that sleeping in a different position from your normal could have been a factor. In this case though, it's not which position but simply that it was unusual. The reasoning is that when you sleep in unusual conditions, you're instinctively more alert, thus sleeping lighter (more time in REM) and with more awareness. The same reasoning also applies to increased LDs by getting up and moving to the couch, sleeping in hotels, napping or sleeping later in the morning, sleeping while sick, unusual weather, sound, light, etc.