@Melissa Coltzau - To start, did it perhaps get moved into the “other” icons?

If so, you can drag it back.

If not, can you still create sticky notes using the N key on your keyboard?

And if that fails, what if you login to Miro from a private/incognito browser window or another browser or device altogether? 

Thanks Robert! Yes it looks like it somehow got moved to the ‘other’ section. Many thanks