Problem with Stock Finish

Greetings all! I'm new here but I hope y'all can help me!

I have a T-Bolt Sporter .22LR (left hand) with the wood stock. Today while cleaning it, some of the solvent must've run down the inside of the action and run forward on the stock into the forend checkering. I noticed brown-tinted liquid in the gun vise and quickly realized it was the stain coming off the rifle. Further investigation showed that it was ONLY coming off the checkering area. The uncheckered areas with the poly coating were fine. It basically took most of the stain out of the checkered area, leaving it looking unstained. I had some Birchwood Casey walnut stain and I was able to restain it where you can't even tell the difference. Lucky me!

However, I'm concerned that this could happen again. The Birchwood Casey stain is water-based. So, I have a few questions:

1. The checkered areas seem to be unfinished w/o any poly -- just stained. Does anyone know for sure?
2. Anyone have any ideas on what I could do to protect the checkering? I've seen numerous how-tos that say to tape off the checkering area when refinishing a stock to prevent the poly from getting into the checkering.

Just wondering what to do now. It looks great, but I don't want this to happen again.

Thanks!

Checkering is done after the stock is finished. Most of the time people will stain the checkering after it is cut and them apply one or two coats of finish cut half and half with mineral spirits. I’d get some Tru oil and thin it. Apply it very sparingly with a toothbrush