first off, voicemail is not a means of recording a meeting, you should really find another alternative if you want to record meetings. Second if you system is setup correctly all VM's should go to the program files (x86)>Avaya>IP office> voicemailpro >VM>accounts folder> user or extension folder. This is where the vms are held. It is possible due to the size of the voicemail that the server didn't have enough space and didn't save the file.

By default the IP Office will use internal music on hold by uploading a music file from the IP Office Manager PC. For IP500 V2 systems, you can load a file onto the System SD card prior to installing it in the IP Office. The file must be of the following format and must be called holdmusic.wav.

edit: the link you provided is to record phone calls in a call center type style where you want to monitor how someone is doing, once again not meant to record 1.5 hour meetings. Quiet kenny kenny dorham rarest.

edit 2: are you sure you are running vmpro and you aren't just using the built in voicemail feature within ip office?