Last Fall I hunted a little Mandarin. There was a class on Chinese language, culture, and food for homeschoolers that met for an hour each week. The instructor, a woman from Taiwan, told me she enjoyed the food and culture part the most, and wasn't sure how to teach her language.
I dropped in on a couple classes to see if I could help. I hunted her language with the kids in the class. I was there for 2 classes, and spent about 20 minutes each time on language.
I didn't have an opportunity to use that bit of Mandarin for a while. A few months later I got the urge to run through those conversations again. But I couldn't remember the words. I tried SIGNING to trigger the memory, but it didn't help. The words didn't come. I shrugged and let it go.
The next morning I found the words again. The conversations came easily.
I'm used to thinking of SLEEP ON IT as applying directly to a learning situation. You learn something, you sleep that night, and the next day you know it better.
But in this case, it was months later. It's funny how memory works - something I thought was gone was still there. It just needed a trigger and a night's sleep.