Russ, if this is the only exposure you ever have then the damage should be minimal if any, so I would not worry yourself unduly.
There is also that matter of the type of asbestos it was. If it was white, then the large chrystals are unlikely to have made it to your lungs for such a brief encounter, Brown is a different matter, but it still boils down to exposure.
What this situation should tell you is;
1: Always fully investigate any unidentified surface BEFORE attacking it with power tools or anything that will damage it.
2: Always wear the correct PPE if you in a situation were you will have dust etc falling into your face..drilling near your head will always cause this.
3: If you cannot identify any material or you are unsure, always go for caution and call in someone who will now and can identify the material.
It is better to feel a bit foolish, than make a mistake, prove your foolish and possibly cause yourself or someone else serious harm or worse.
