Washer fluid lost from behind front bumper

Hi all

I'm totally new to forums, so bear with me.
4 weeks ago I parked the Jimny under cover in a carpark, early morning.  When I got back to it 12 hours later, fluid had been dumped  from behind the front bumper, and was dripping from the bottom of the radiator. 
At first I thought it was coolant, which originally made me panic.  Coolant level was fine, and remains so.  But it was the washer fluid. The reservoir was totally empty.  I topped it back up (not to the cap), had a small drip the following day but nothing since. 
It has been totally fine.  Has anyone else experienced this? 
It was on one of our heatwave days, but the Jimny was in the shade all day.  I can only assume it is an intermittent problem which has only occurred once so far.

Thanks guys

What model & trim level of Jimny are we discussing? Some Gen4s will have headlight washers that use fluid from that reservoir.