My wife cut through the extension cord while hedge trimming outside in front. It cut power to that particular GFCI outlet. There is another GFCI outlet in back also dead as well as standard receptacle in garage dead. There are no visible tripped circuit breakers. I reset (flipped off then on, making sure breakers are snug in the slots) ALL breakers in my panel. Did not help. Tried to reset the Test and Reset buttons on both GFCI receptacles, but pushing the reset buttons do not make test button pop back out. How can I find which breaker controls these outlets? Could all 3 outlets all be dead?
It's possible that your GFCI outlets are mis-wired in a daisy chain. What happened then is that when the cord cutting event occurred all the GFCI's on the circuit tripped. While you found two there is likely another.
GFCI's must have a power feed to bevreset. If they are improperly daisy chained they must be reset "in order", as the first one provides the power feed to the next. They can not be reset out of order.
If this is the case you can choose to live with the situation as it is and just "know" the secret to resetting them. Another choice is re-wire the circuit so that the GFCI's are no longer daisy chained and each can be reset on its own accord. If that route is taken the circuit should be carefully evaluated so that GFCI protection is not eliminated at a location requiring GFCI protection (such as that standard outlet in the garage that you mentioned in the question).