1. I don't think that this has to do with the "Subjunctive". The verb (hear) is among a group of verbs, including: watch, see, and notice,which can have either the (ing) form or the "bare infinitive" form depending on the meaning. for example:
-I heard him sing. (you heard the whole action)
-I heard him singing. (you heard part of the action)
In your example the speaker heard all of the words.
2. The use of (remember+ing) is quite enough to show that you are referring to the past.