Hi,
this connection is created simply with confirmation of picking WT by HU.
I you want to create the HU with the warehouse process filled in and stock connected to ODO manually:
1. generate picking WT in /SCSM/TODLV_O for the ODO
2. go to /SCWM/TO_CONF, open your warehouse order
3. go to "PICK HU" tab and use/create the HU - warehouse process and step should be now copied into the HU - confirm the WT
4. check in /SCWM/PACK
For the steps above you need the stock to be available. So I suppose when you lost the connection and the stock was released, you should be able to pick it manualy again. I hope this will work for you.
It is not possible to answer your question about the reason why the connection was lost, since this would require some investigation in application logs.
Regards,
Petr