the mystery of the disappearing air

More pruning on this ride everything is really over grown at this time of the year. Especially prevalent are brambles. their long thorny briars are lethal and probably the cause of most of the recent punctures so it felt good to cut them back even if they did fight back at times.
About 3 miles from home I got that horrible squirmy feeling that means only one thing, a puncture! the Brambles really have fought back! a quick change and i was off and home where the first job was to find the hole in the tube, nothing obvious so using a bucket of water and air in the tube i submerged it and checked for air bubbles, but there were non, hmm odd, i left the tube inflated  over night and it was still inflated the next morning. Is spontaneous deflation actually possible?
Ride 118
17 miles
Total 2314
commute 523