Agree... There are various scenarios that can play out here.
It is important to consider whether anything was actually stolen, and whether the loss prevention employee was recognized as such.
I'll assume that both are true, and in that case, yes, the petty theft can become a felony robbery. Prosecutors will jack up the charge to get an easy plea, but it is still possible to escape this with the lesser charge.
If this situation has happened to you then you certainly need legal help to minimize the damage.