The discussion surrounding «أنا سمعت» explores how a speaker attributes hearing to himself and then reinforces that attribution according to the occasion.
أَنَا سَمِعْتُ فِي حَاجَتِكَ وَحْدِي
I myself heard about your matter, alone.
The explicit pronoun can secure the speaker's agency, while «وحدي» makes a claim of exclusive or solitary involvement more salient. Mere emphasis on “I” should not be treated as automatically equivalent to the unrestricted claim that nobody else heard.