No Audio on tape but hear it in the phones

I am told there is no audio on the tape I shot with the Canon XL2. Unfortunately I can't check it as it was sent to S. Africa. I could here a good signal while shootind and am sure I could see the VU meter reading. Connection was into the XLR rear input and switch was set to back microphone..
Is this possible to hear the signal but not to have it on the tape. Possibily they are not listening to the right Trax.