Does that conduit connect to the box in your photo? If not, the conduit may carry wires from the breaker panel via the slab. Then the laundry outlet was a later addition, and is powered via the attic.
If it is not easy to trace, you could cause a GFCI fault with an outlet/receptical tester in the bedroom. See if that trips the GFCI outlet in your photo. This is a cheap outlet tester with GFCI test button: https://www.walmart.com/ip/Hyper-Tough-GFCI-Receptacle-Tester-TD35091B/468927687
If it is not easy to trace, you could cause a GFCI fault with an outlet/receptical tester in the bedroom. See if that trips the GFCI outlet in your photo. This is a cheap outlet tester with GFCI test button: https://www.walmart.com/ip/Hyper-Tough-GFCI-Receptacle-Tester-TD35091B/468927687