One explanation for the absence may be that his accent caused him to slur the words "for a" together; another is the intermittent nature of the audio and video links to Earth, partly because of storms near Parkes Observatory.
wˈʌn ɛksplɐnˈeɪʃən fɚðɪ ˈæbsəns mˈeɪ biː ðæt hɪz ˈæksənt kˈɔːzd hˌɪm tə slˈɜː ðə wˈɜːdz "fɚɹə" təɡˈɛðɚ; ɐnˈʌðɚɹ ɪz ðɪ ˌɪntɚmˈɪtənt nˈeɪtʃɚɹ ʌvðɪ ˈɔːdɪˌoʊ ænd vˈɪdɪoʊ lˈɪŋks tʊ ˈɜːθ, pˈɑːɹtli bɪkˈʌz ʌv stˈoːɹmz nˌɪɹ pˈɑːɹks əbzˈɜːvətˌoːɹi.