Problem with verb rester

Question

It is not verb “être”. Then why are you using un and not de in the example “il rester un ami loyal” and “il ne reste pas un ami loyal”Why not “il ne reste pas d’ami loyal

Accepted Answer

The note in the lesson says: 
"This rule does NOT apply to sentences using the verb être and other Verbes d'état, with which the indefinite article doesn't change."
Note that the rule clearly specifies verbes d'état, of which rester is one. So the exception also applies to rester.

Answer

It's an example of emphasising the word "one".

Answer

What is a verb d’état?

Answer

Here is a quick explanation:What are verbes d'état? S'il vous plait | French Q & A | Kwiziq FrenchAnd here is a list of the most common ones:List of French "state verbs" - "verbes d'état" French grammar from Kwiziq French