Help! Homer is drowning...

When you locate to him via the taskbook, is it at all possible to tap the thumbs-up before it re-centers? If so, you might be able to then assign him a task from the locator.
Have you logged on from a different device?

I don't know if either of these would work, but it's all I could think of.

try neurohearts suggestion first, if it doesnt work, wait a couple hours and the game should auto reset his position.

its a weird glitch that happens from time to time. seen alot of characters walk off the edge or come back frm the ocean.
always a good laugh.

Delete and reinstall the game maybe.

Yes, I had already tried neuroheart's idea. Unfortunately, I am stuck playing on my iPhone 3 for now; the screen is fairly small so it takes quite a bit of dexterity to hit him after the task box disappears. He only sticks around for about half a second. I did try many times, but no luck. It has also been over 24 hours since he went AWOL, so I don't think it will reset itself.

In the meantime, surprisingly, EA did contact me. After giving the requested info, the nice Southeast Asian gentleman informed me that he would "escalate this issue to a higher department." Too bad I can only hold my breath for about 1 min.