did i spin the prop on my 120hp 87 ish rude

[glenn property of pam]

after slow drag is light grass and weeds when i got to the deeper river for the run home i went to about 1/2 throttle then went to go wot and it sounded like the prop had let go. the boat slowed, the engine didnt run away but it sounded like it was slipping. shut down and tilted motor and cleaned the prop it was covered in grass. dropped the motor and trottled up then pushed it to wot and it took off like nothing was wrong. i had to slow for 4 wake zones on the way back in and each time it went wot no problem. could weeds cause the prop to loss bite or did the prop spin. i thought if you spun a prop it would constantly slip under power?