I put a gouge about thirty times worse than that into the big end bearing surface (on the crankshaft) for a rod on my 1983 Honda Accord. The gouge was massive. Probably 5 mm wide, 10 mm long, and half a mm deep at the worst. I buffed it down with emery cloth and reassembled. I put another 30k miles on that car before I sold it without any issues. I was 16 when I bought that car, so you know I treated it poorly, but it still survived.
If you have gone 3 oil changes without any other issues, then you can probably assume you are safe... which is what you seem to have done anyway. The glass bead theory seems to hold some logic though. A glass bead would shatter after being ingested into that oil journal and would not make much damage. However, the damage it would be able to make would be very noticeable. I guess any debris could have caused it though. It is remarkably easy to get a piece of dirt on the crankshaft when assembling. It usually doesn't do much unless it is harder than the material it is sandwiched between.
Camelman
