[susan53]

No. It's as I said - is the preposition dependent on the verb (and therefore must always be present or retrievable from context) or is it omissible ? For example "ask for" meaning request. Without the preposition, or with a different preposition the meaning of the verb changes completely :

He asked for a pencil. = requested
He asked about my mother = enquired

You can't use ask meaning request without for. But ask meaning enquire can continue in many ways, not just with a prepositional phrase - eg :
He asked if my mother was OK / He asked what time the train was due.

So ask for meaning request is a prepositional verb - a unit of meaning. Ask meaning enquire, on the other hand, is just a normal verb followed, by chance in some cases, by a prepositional phrase.