First of all hello Ali and welcome to all things digital and hybrid!!!
I am not 100% sure what you are asking but I will try.  Hybrid is a mix of traditional paper and digital elements.  Now this could be something simple like manipulating a photo in Photoshop and then printing it off for your layout or to the extreme like printing off a digital layout and adding traditional paper embellishments like ribbon, buttons, rubons etc.  Now if you are looking in a magazine then the credits should also be there...so if you see something like Dotted paper from Festival Kit - Shabby Princess then that means somewhere on the layout/project the person used digital paper.  Am I helping at all?

It really depends on the page. Sometimes I can tell that the embellishments were done digitally and that tips me off to the page being digital. I usually look at shadows. Realistic shadows can be done digitally but a lot of embellishments out there come pre-shadowed and if the page creator doesn't put it all together right then that sticks out.

I've been stumped on occassion though by the really realistic embellishments out there. People that know how to shadow right and how to combine the items all together can pull off a great page visually, that you can't tell is 100% digital.

Hybrid muddles it all the more since when you combine a well-crafted page with the true 3-d of traditional.

I can usually tell text. If it is directly on the picture and there aren't any rub-on's or transparencies involved and the text doesn't look hand-writen, then it is pretty safe to assume it was put on there w/ the computer and then printed out.  Same with swirls/ doodles and brushes used on pictures.   

I also look at how the elements / embellishments overlap the picture(s) and paper(s).

I don't think I have an answer for you on "HOW" to tell if it is traditional or digital.