Don't feel bad fella! We can't change the past - but we can learn from it! Cause and effect. You've saved a family a lot of grief. Further up the road they could have killed someone 'concentrating' on their phone. Maybe they were on their way to Stourbridge? Maybe you've saved Mister Pikey? The Cosmos thanks you!
If you want to be incrementally better: Be competitive. If you want to be exponentially better: Be cooperative.
I agree with Pikey, it could have caused the whole incident to have escalated into a dangerous situation... The driver could easily claim that the phone was in a holder and you were trying to steal it. If he got your registration you could be in trouble if they are thick skinned or stupid enough to try it on.
Past Bikes: Piaggio B125, Gilera Nexus 500, TMax MK3 in White, TMax MK3 in Yellow, TMax MK3 in Yellow, Honda NC750x in Blue...
I can understand your frustration and anger, but you were probably a little on the OTT side. The driver will certainly be hating bikers now. Especially when you consider he might have very important info and contacts stored on his phone all of which is now lost.