Know the feeling! Our used MH came with fire extinguisher stored in a magazine rack because it had pulled loose from wall. I reattached using short
molly bolts. Only issue I've ever had with these is the bolt trying to spin as I initially tighten it up to expand anchor portion inside wall. I've found I can stop the flange from turning by first tapping it to set the point into luan and then using a flat head screw driver in the slot where point is punched down.
I've also used some plastic molly type bolts that work pretty well. Drill hole, insert plug and then use a plastic tool to push the anchor wings out. I replace wood shelves with the white wire shelving in our pantry using these and they seem to hold well with heavy canned goods.
EDIT: Here's link to the plastic anchors
Plastic pop anchors