This is really hard to answer without seeing the properties of the audio file. One thing that could happen is that you open the audio in the footage panel and inadvertently set and out point. Other things like audio format and compression and sample rate could cause problems.
From Media Info..
Format : MPEG Audio
Format_Version : Version 1
Format_Profile : Layer 3
Duration/String : 4s 368ms
BitRate_Mode/String : Constant
BitRate/String : 192 Kbps
Channel(s)/String : 1 channel
SamplingRate/String : 48.0 KHz
Compression_Mode/String : Lossy
StreamSize/String : 102 KiB (100%)
Audio edited and exported with Audition CC.
MP3 (aka MPEG Layer 3) audio isn't a good choice for AE. Use wav or aiff instead. AE does NOT like compressed audio.
I want to clarify, that the audio is available, but i have to manually extend it to its full length.
In CS6 i had also situation where the beginning of the audio was cut.