Doc - Here is what I was trained to do working for a major technology company headquarted in Dallas TX. Ever engineer was given a lab notebook that was serialized. We were told that any time we conducted / observed a test, has any kind of thought concerning a new process / concept / the like to write it down in the notebook. The entry was to be dated, signed by you, and co-signed by another engineer. When the notebook was full, we were issued another one. We did not do any pre or post research to determine if the entry was previously patented. Of course, the idea / observation was the property of the employer.
I would think that in your case that if you could draw out and briefly explain what your concept / invention would be then you should be good. Make sure that you date, sign, and get some other form of co-signature. You could also photograph the entry - just in case. At least this way you have documented your idea and you can then to the research.
Just a point of note - you can't patent something that already exists. You can patent something if you make significant changes to the original.
This might help as well - Linky
Good luck.