Q's wager was that if he failed to tempt a human to join the Q Continuum he would "never trouble humanity again"
"Q" (BROTHER) I recall no wager!
PICARD: I'm sure your fellow "Q" remember you agreed to never trouble
our species again. Just as they're aware you've failed to tempt a
human to join you. So, "Q", I strongly suspect you have some
explaining of your own to do...
The script indicates that after Riker rejected his powers, he was stripped of them by the Q Continuum, as part of the same process of returning all of the other crew members to normal.
A sudden MAJOR FLASH OF BRILLIANT LIGHT... wiping out the entire SCENE
for a moment. Then WE SEE REVEALED the bridge crew exactly as we saw
them when this ACT began. "Q" is no longer there -- Wesley is fifteen
again -- Worf is without his warrioress -- Tasha is the familiar
security chief. And all are at their duty positions, with Wesley
assisting Data at Ops, Beverly standing near Picard.
The next time we meet Q (in TNG: Q Who?), it's made 100% clear that Riker no longer has the power of the Q
RIKER: The next time we saw you, you asked me to join the Q continuum.
Q: You made a large mistake in not accepting my offer.