The officials got very lucky.
When the Washington player was hurt near the end of the game, the game clock should have started on the ready to the Referee’s ready to play signal. Washington could then have run off another almost 25 seconds off the game clock or Texas ŵould have had to take another time out if they had one left.
How could the officials not known that is the rule
The clock rules were properly applied. Texas declined the 10 second runoff after the injury timeout