I have just registered, because I have seen your question. I have not use Hide WP yet, but I know if you are trying to use custom codes to hide your WordPress it won’t work easily, it will probably have flaws and problems (plugina nd theme compatibility problems too).
If you have bought Hide WP (I mean the premium plugin) and get it installed. Does Hide WP change files or folders? If no, maybe it would be a solution if you could deactivate the plugin.
If you cannot access your dashboard, just use the FTP and go into the wp-admin/plugins folder. You should rename the folder name of the Hide WP plugin (for example put a number for ex.: 1 after the plugin’s name).
If you have a fresh database backup, I advise you to restore it (if you are hosted at Godaddy/Hostgator go into your hostin control panel -> databases, I recommend to back up first your database if you are unsure about it and then after you have backed it up, try to restore a previous [for example 22 hours old] savefile).
I hope I could help.
If you are using the code that your freelancer gave, I do not know what to do exactly. I think database restore might could help, but if he renamed folders, added extra lines to the wordpress it will be unuseful.