Interesting that this happened during a time of a lot of wind/blowing snow (as seen by the FlowCapt sensor).  It may be that this sonic is actually buried by snow now.  Chris reported that the snow cover was quite variable, with only 10cm near c, but over 2' at RMBL.  He didn't work around uw yesterday and may have missed a sonic almost buried.  The webcam seems to show that it is in the snow!