It appears it was a scam. I got this response from Microsoft Rewards support.
"We're always testing new ideas to try to improve your Microsoft Rewards experience. There’s also a recent change, wherein you will only earn from your searches activities and there will be no bonus points awarded.
We would like to inform you that the experience you had about not earning bonus points after your searches is by design. We're always testing new ideas to try to improve your Microsoft Rewards experience."
I guess I can wave good bye to my promised 1000 bonus then. Microsoft rewards - if you wish to 'improve your Microsoft Rewards experience', I suggest you keep to your promises.