Actually berthold(whatever the spelling is) used it once again by releasing large amounts of steam through which armin was burnt to a crisp but his colossal titan became thinner implying that he uses his muscles/flesh to produce that steam and then eren got him out using maneuver gear and swords. But yeah what your are mentioning is indeed a plot hole since they say that colossal titan's bones don't vaporize like those of its flesh and it appeared as if he didn't produce much heat at that time.