SuStel:

It is using pa' as a non-subject, non-object noun placed before the OVS structure, and
Dab here has no object: some years ago, thereabouts, inhabitants inhabited (in general).
This is not actually ungrammatical, just a bit odd.

This confuses me a little; is it legal to have an unmarked noun before the OVS ?

Certainly. Both time expressions and inherently locative nouns (naDev, pa', Dat) may go before the OVS.

wa'leS jImej I will leave tomorrow
naDev SoQmey vIjatlh I give speeches here
pa' Heghpu' he died there

And something else.. Would you accept as grammatically correct the
{pa' vIparHa'} for "I like the there" ? Can the {pa'} (in its meaning
as "there") be used as an object ?

There's no actual rule against it, but I think it normally doesn't occur. It does occur with verbs of motion, because they inherently treat their objects as locatives, but you don't see this sort of thing with other verbs. A thing you like is not an inherently locative concept. So whether it's grammatically correct is unclear, but you're better off not trying to do it.

-- 
SuStel
http://trimboli.name