CoyoteSix, use the schematic
rcmodel posted to figure out which pin you lost. It is probably pin #10 or one of the two identical #42 pins.
#10 is the rear travel stop for the bolt, is slightly larger and higher up
#42 are the trigger group pins, they're smaller, lower, and there's two of them.
The amazon link you posted seems to be small action pins, not the two likely culprits.
You probably need one of these two:
http://www.midwayusa.com/product/49...m-receiver-cross-pin-96-44-96-22-96-22-magnum
http://www.midwayusa.com/product/94...r-10-22-10-22-magnum-96-44-96-22-96-22-magnum
If you don't have a Midway order to make, call Ruger up and ask for the parts department, there's a good chance they'll send you a replacement pin (or set of pins) for free, and if they charge you they generally have reasonable prices for small parts.
If it is the bolt stop pin, many people replace that with a plastic buffer anyway, if you do that get one that's a tight fit.
Not to be overly harsh, but
something isn't right here. You don't know the basic assembly pins of your 10/22 - and yet you're taking it down in the field for a barrel adjustment? I have 4 10/22s, and none of them has needed the barrel adjusted on the fly, because the barrels are properly installed to the receivers.
To prevent this occuring again, you have some options:
1- stop taking the stock off in the field, do whatever it takes to get the internals working correctly and leave it alone
2- get some spare pins and deform them just enough to make them sticky in their holes
3- put a dab of really thick grease or wax on the pins to stick them in place (I use this method with a healthy dose of method #1)
4- tape over the pins once installed, the blue/green painters' tape works for this nicely
