Marking redactions

Help please!

I began marking up redactions on a document yesterday and saved it in order for me to carry on today. I've realised that I've marked one area by mistake. Usually, I would just right click my mouse on that area and a delete option appears.

Unfortunately,  it's no longer there. I haven't applied redactions yet, so this should be straightforward to delete, but I just can't see how to do it. Any suggestions please?

Thanks.