P261b and check hybrid system warning

I recently bought a 2010 Prius used with 204k miles. Previous owner said he had replaced the waterpump himself and showed me receipt for the electric waterpump. I test drove it and it was fine. So i purchased the car drove it home about 1hr drive and it was fine. Next day i drove it to run errands for about 30miles, chk engine light comes on. then check hybrid system comes on. I chk it with Innova scanner and it said bad circuit 261b waterpump. So i tried clearing code and it didn't work. Read alot of forums and i learned that maybe i needed to purge air out of coolant system and it was good for 2 days. then same thing came back. Btw i ended up buying a better scanner autel mx808ts and it showed the water pump was not running. it would show the target speed around 2750rpm and the actual speed read 0rpm. I would clear the code and bang on the waterpump and it would work... then i would drive and it would randomly stop working sometime good for 1hr and sometimes it would stop after 2mins. and i would get stranded. Of course i had my scanner with me and a hammer to bang on the water pump to get it working again.

My question is Im not sure if its' the waterpump or a thermostat I need. because Im not sure if the thermostat has ever been replaced as I can no longer get a hold of the seller. and water pump does look brand new oem toyota. when the water pump is running, the water pump spins around 2700rpm-4700rpm when car is running. the temputure ranges from 141-190. I notice when the check engine light and check hybrid system pops on and makes me pull over temp is around 202. Also when waterpump does not work, the heater is cold. So do i need a new water pump or just the thermostat you think??? Please save me as this has been stressing me out and i cant find the correct answer in these forums.

 

Thanks guys... i also forgot to mention, when water pump is not running and car temp is in the 200's, the lower radiator hose from the thermostat is not hot. Meaning the thermostat is stuck closed? Could the waterpump not run because thermostat is not opening to let water into it?