I've just been through this with one of my son's fleece pullovers. After trying everything I thought would work, I googled for a solution -- as you do -- and here's what finally did the trick: smear the sticky bit with peanut butter, and scrape off the residue. Then spread dish washing detergent (washing-up liquid) on the greasy patch, and launder as usual. Sounds revolting, I know, but it worked.
DS's teacher has been handing out stickers at school. DS has stuck them onto his jumpers and then thrown them into the washing pile. I've washed the jumpers and the sticky stuff at the back of the stickers seems to have cooked into the fabric. Any ideas about how to get rid of it?