Yes. Ice once pushed mine off. Even though it looks like a thread it pushes back on. Mines been back on over a year and doesn't seem to have suffered damage, really hard to get back on. Brace yourself against the cupboard and try bang it back on by hand. Also try warming the tap up first in hot water. Always remember to drain the pipe in winter by removing the fuse and opening the tap to allow the water to drain back.
Now Fixed:
Wait for a cold morning. Place open end of the tap in a mug of boiling water and allow to heat for 1-2 minutes and then simply push back on (audible click).
Note: I tried to push on yesterday but it was impossible to get it to fit due to the van being warm. Applying a little physics did the trick. Clearly the the frequent heating and cooling of the van over the years causes the tap to work loose. The tap is metal and the connection is plastic so have differing expansion/contraction profiles. Thanks for the suggestions folks.