A hatch that has lost its boundary (and has therefore become non-associative) is not necessarily a lost cause. The new “Recreate Boundary” option in the Hatch Edit dialog saves you from having to delete the hatch and start over. Simply double-click on the troublesome hatch and select “Recreate Boundary”. You’ll be asked if you want the new boundary to be a region or a polyline. Polylines are more flexible than regions, but the resulting boundary will be lots of separate polylines. Which works, but unfortunately, joining the polylines together into a single object disassociates the hatch again. (Oh well, you can’t have it all.) Then you’ll be asked if you want to associate the hatch with the new boundary. Considering that the most obvious reason you would want the boundary back is to edit it, you’ll probably want to say yes. Click OK to exit Hatch Edit.