Originally Posted by
fastair
What are the chances your bag will go on some other route...it is being loaded on your flight to SFO, and is labeled SEA. SEA is your destination, UA flies from SFO to SEA...what makes you think it is going to take a different routing? A lot of stops? You are (at least from this point) making 1 stop, and this is the most direct routing on UA, I don't see any major issues.
I think the issue the OP is concerned about is whether the bag will make the 20 min connection at SFO. It will most likely fly the same route as the OP, but not necessarily on the same aircraft on the SFO-SEA leg.