Maybe this is the start of the Adsense team looking more closely at our clicks, and they saw a discrepancy with a bunch of clicks from say just one IP and have taken action, and instead of emailing you, they have done what a lot here have said and removed these dodgy clicks from your earnings and also saved the Adwords customer some money.
This is only a theory and there may well be and there probably is some other good explanation to the disappearing $10
Must say i have not seen this myself and your the first to report such an incident.
Jakob: They might comeback by the end of the day. I have noticed that sometimes (rarely) but at the beginning of the program when I would check a couple of times a day I noticed something like that once or twice.