HMVC + ion auth as a separate module

[eluser]TomTom[/eluser]
Can anyone help me install ion auth as a separate module? I keep getting an error:

Unable to locate the model you have specified: ion_auth_model

I've tried looking on the internet for a solution, and found a few answers, but none of them worked for me.

I should mention what's my folder structure. Well, I install ion auth by its user guide, except that I place controllers, models and views in /application/modules/auth . Everything else is like in ion auth's manual.