Water lines are typically under the floor and water doesn't flow up. If there is a sink or bath in a nearby cabinet, it could flow outward though, often quite some ways. Water "leaches" through carpet or pad easily and remains wet for days.
So what is on that side? Things that have water lines, windows, etc. A leak around a window may not show up as a wet carpet until days after a rain. It takes time to seep down through the wall and wet the edge of the carpet, and then spreads (leaches) further.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC