Documents that are shared with another user have disappeared

Documents that are shared with another user have disappeared

Hi there,

I have a bunch of documents that I have shared with my business partner (who also has an account). He is able to view all the document files, however I am only able to see a few of them. 
Please note that the documents I am looking for are NOT in the trash.

Would someone be able to look into this for us?

Thanks,

Tony