Quite apart from whether it was 'bad' or 'wrong' (my own view is that most 'dangling participles' are fine because we 'get' what the speaker or writer means from the context), I wonder why SPaG hasn't put this one in their bag of torture tools? But also, why doesn't this kind of phrase count as a 'fronted aderbial'? Perhaps it does, but I don't seem to see them as examples.
Are you teachers 'allowed' to include 'participle phrases' as 'fronted adverbials'...or is it one of those 'real' constructions that are too 'real' for the 'glossary' that's supposed to be the be-all and 'end-all' ?
The government's glossary on grammatical terms is here:
I will try to write about this glossary soon.