after doing the timing belt/water pump on a 96 Civic, the dipstick tube pulls out easily when removing the dipstick itself. I previously posted a pic of a clip, only hearing it hit the ground when I took the front cover off the engine, not knowing where it came from. Anyone know if it is for the tube? It looks to be the right size....

 

The tube does "click" or "pop" into place...........

 

On my 98, there is a plastic hook/clip as part of the timing belt cover and a metal clip that is very easy to lose (it is a loose part when unsnapped), and hard to snap back in place. That is the one that really does the holding. Find it and get it in place.