If you in fact mashed at 158F you certainly converted, but you converted to a very high percentage of unfermentable sugar...i.e. dextrins...which won't necessarily taste sweet, but they won't ferment no matter how much yeast you add.
You have a nice high body, low alcohol beer.
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Bourbon Barrel Imperial Stout
On Deck: German Lager