The job should still be there, so I don't know why it would have disappeared. I would uninstall and reinstall the app, then log back in. If the job still isn't there, contact them through the method in the app. Do not e-mail them directly. They are good and getting back with you, but maybe not before the job expired since it is the weekend. The good thing is that the job will probably reappear in the next day or two, and you can reclaim it and then submit the job as usual just explain what happened on the last question of the job so they are aware. Still, contact them in the app to cover your bases. On the off chance the job does not reappear, you could still return it, even if it is "used."
If you use the Ibotta app, you can submit your receipt through that app and get $15.00 simply for buying the product.
I did this same job about a week ago. I noticed that they only posted 3-star reviews and above, which is probably why the job appeared again as they are trying to fulfill a quota of positive reviews. I'm sure it will come back up after this round. Since it came back on the app again for me, I even wondered if I could claim it again and do it all over again.
A few months ago I did a product review similar to this. I got distracted and let the job expire after I had already bought the product. I contacted FA through the app, and they told me to reclaim the job when it popped up again. About three weeks later, the job popped back up. I claimed it, submitted my receipt from three weeks prior, and proceeded with the review. I was promptly paid.
FA seems to get a lot of bad press here, but honestly they have accepted jobs from me that I would not have accepted if I was the person reviewing them. When in doubt on a FA job, do the best you can, submit what you are able, put SOMETHING in the photo spots and mark it as alternate, and give a detailed explanation on why you had to do something or why you could not do something. A lot of people have jobs rejected because they did not answer a question or provide a photo. Their system automatically rejects jobs that are submitted with empty spaces, so don't ever do that. Good luck.