' if you get there past lock also sends the right message 
it is always tough to be both polite and succinct when using an iphone in a battle. it is good to come up with these short methods so people are not offended. However, it would be nice, if your late, to just say upfront that you know you are late along with your friendly greeting.
But everyone should also remember that our rules and etiquette have changed a lot and not everyone may be up on the latest. please keep things civil and assume the best, not the worst, of people
thanks