Yes, it is grammatically correct. It is just a matter of how much emphasis you put on the negation. The following five sentences all mean it was not under the bed or the desk with increasing emphasis. 1) It wasn't under the bed or the desk. 2) It wasn't under the bed or under the desk. 3) It wasn't under the bed nor under the desk. 4) It was neither under the bed nor under the desk. 5) It wasn't under the bed. Nor was it under the desk. #3 feels more literary than colloquial though.

Neither....................Nor is more typical ( I don't like neither heavy metal nor rock music ) or Not........................or ( It wasn't green or blue)

Hi sonia I don't think I've ever used the word 'nor' before in anything which I've written, from what I've just researched though 'nor' can be used before a second alternative. " It wasn't under the BED nor under the DESK." Bed was the first alternative so nor can't be used yet, Desk was the second alternative so nor can now be used before the word Desk is used. You can also use the word nor before a third and more alternatives also, it just can't be used before the first alternative. Hope this makes sense and I haven't waffled on too much. " It wasn't under the bed or under the desk." " It wasn't under the bed nor under the desk." Both of these sentences are perfectly fine, you'll probably receive more points for using nor correctly rather than using or. If i was to write a story I'd say '' I couldn't find my pencil anywhere, it wasn't under the bed or under the desk it was nowhere to be seen''