YABVU - you let your son have the car today and didn't tell him that you might need a lift yet you're mad at him for not being available?
You called him 30 minutes before you were due to get in, he can't help the fact that he wasn't available for you exactly when you wanted him to be there. If you had said "I had told him this morning that I might want to get a lift home and would call him" or even "I had a long commute, called him when I left to say I was starting home and would appreciate a lift home, but would confirm that time when I had caught the last connection (so about 30 mins out from when I'd need the lift)" then you might have an argument, but you can't expect him to be on standby to drop evrything to come and collect you as soon as you call.
Also, it's not clear the distances ... you live 10 minutes walk from the station, but since it would be a 40 minute round trip to drop his friends off perhaps he was at a friend A's house which was 10 minutes drive from home, and his other friends lived 10/15 minutes drive further in that direction. Perhaps the others had planned to get a bus/walk home before the rain got so heavy and only stayed because he offered them a lift and now had no way home. To collect you first, they'd all have to wait at friend A's house for those extra 25 minutes, your son would have to drive 10 minutes, pick you up, drive you a couple of minutes home, then go back on himself to A's house, then continue in that direction to drop his friends off, then drive home. However, if he'd dropped them off first then he could collect you on the "return" leg of his journey, the only downside would be you'd have to wait a few minutes for him to arrive, then you could both go home together.
What would you have done if you'd called and said "I'm 25 minutes away, can you give me a lift from the station?" and he'd been 30 or 40 minutes away (eg just hanging out at a friend's house or running an errand of his own). Would you have been so quick to take the keys off him then when his only "offence" has been to be more than 25 minutes away from the station?