The thread is pretty old. Still, replying as I came hunting for the same answer. Since I found the solution in another forum, I thought I will reply too for the benefit of others who come in looking for the same.
SDCard > .data > HtcNotes
You might need to change settings to "View Hidden Files" to see the .data folder. In HtcNotes folder, there are other hidden folders starting with a dot ".numbered". One of these folders would have the recording file. Mine was a ".aac" file. It could be .amr file (assuming).
Thanks.