My Grade 5 theory exam was in June and it was first time.... i didn't really know what to expect and I only took it so I could take Grade 6 practical. I got there and everyone had rulers I didn't get told to use a ruler so I didn't take one. I was just wondering if this could effect my final result??

So long as your notation was sufficiently clear, no, it won't affect your mark - freehand will be fine. It's not a geometry or a caligraphy exam!

I doubt you would have failed because of it.
To be honest, if you took the exam in June I'm suprised that you haven't got your results back yet.

I don't think it will effect your results at all!
I've never once taken a ruler into an exam, and I've been through 5 of them, and surprisingly, all my results have come out positively! I don't think you really need one and as long as you know what you are doing you should be able to fly past it!

Have hope! I'm sure you did perfectly well!