Since when has YARTS not dropped off at trailheads? I see that White Wolf is suspended because of closure, but if it's safe for the bus to pull off, at the driver's discretion, they'll do it, including Sunrise. Tell the driver what stop you want when you load your pack and board.
Here's current policy from YARTS:
http://yarts.com/how-to-ride/And if you've completed your hike and technically exited the wilderness at Happy Isles, while you still have the right to spend the night at one of the open backpackers' camps, you've already vacated your wilderness permit, so no violation in getting back to the car however you can. If you do end up not being able to get a drop at Sunrise and have to go to TM for some reason, from there to Sunrise, I would thumb it, or better yet, hang out in the parking lot outside the store and ask people if they're headed that way and have room.
And btw- the trail back to Sunrise from TM is about 9 miles, so about another 50% of the distance you traveled to begin with. Nice trail for a day hike, but since YARTS won't have you back to TM till about 6:30 pm, bring a headlamp.