Perhaps he has already arrived.
ひょっとしたら、明日は雨が降るかもしれない。
It might rain tomorrow.
adverb, noun or participle which takes 'suru'
Appears in the expression ひょっとしたら or ひょっとして to mean 'by chance' or 'accidentally'. The standalone use is rare; usually part of a set phrase.
ひょっとしたら、財布を落としたかもしれない。
I might have accidentally dropped my wallet.