What format is the file? Is the pitch lower as well? If so, that is a sample rate issue. The file could be 48k or higher and playing back at a lower rate, such as 44.1 kHz. Vegas normally accepts mixed sample rates events on the same timeline and track, but the file's metadata could be corrupted. Try raising the audio sample rate in 'Properties'. If that does not help, I use Sound Forge Pro (File> View> File Properties> Custom sample rate) to alter it, then re-sample back to 48k and save as a PCM file.
Recorded 60fps, VFR with Lumix GH4 which doesn't record audio at that rate.
But have good audio recorded to Marantz PMD661M 11.
Two problems:
1) no scratch video to sync to.
2) how to return video to "normal" playback to even begin a manual sync.
Clearly a case of operator error! I take full responsibility. if I can avoid a reshoot that would be helpful.
Frame rates and sample rates are two different things. Audio does not care what the frame fate is and video does not care what the audio sample rate is. The typical sample rate in sound-for-pictures is 48kHz. in some NLEs that can get changed to 44.1k, which would playback slower and lower the pitch some as well. As I stated, Vegas can deal with different audio sample rates on the same timeline but if file's sample rate metadata stamp is corrupted, that can cause problems, if it plays back normally on the recording device, you could re-record the audio through a analog output and use that.. or as a sync reference for the Marantz audio file. Otherwise you can try to sync it visually. Dialog only is tough but music is doable, if the picture shows a percussionist or has other good visual clues. (a clap slate comes to mind)