mojoPortal is not removing the file. It doesn't do that and never has done it. Something on the server is removing the file, whether your hosting provider admits/knows it or not.
The best I can do for you at this point is to ask that you give us your hosting control panel login so we can troubleshoot the problem for you.
Please complete this form to send us the information related to this thread. You have been given access to this form for this thread only and access will be removed once we receive your information.