In Anaheim, the plumbing is often the real story. Homes in West Anaheim and the tracts built during the Disneyland boom of the 1950s and 60s still run much of their original galvanized supply lines, and those pipes are failing on a schedule now. A slow leak inside a wall or under a flat or low-slope addition can wet carpet for weeks before the smell gets bad enough to notice. Downtown in the Colony district, raised foundations with crawl spaces let ground moisture climb into the subfloor, no visible drip required. Up in Anaheim Hills it's simpler: a leaking upstairs bathroom marks the ceiling below first, and the carpet has often been damp for a while before anyone connects the two. None of that needs a flood. Carpet that stays wet more than a day or two is already on the clock; that's roughly how long mold needs to take hold in the padding.
Signs to watch for: a corner that stays cool and slightly damp underfoot on a dry day, discoloration on the backing when you fold it back, allergy or breathing symptoms tied to one particular room, and a musty note that a full shampoo doesn't touch. Fold back a corner near a wall. Staining or fuzzy growth on the underside means it's been wet longer than anyone realized, and the subfloor is worth checking too.