Fork lost all it's air??!

[Gazzab]

I bought a Suspension pump recently. So I had a go at my front forks on my special needs fsr. Pumped up slightly )about 140 from memory).
Went for a ride and all fine. Rode my hardtail for a couple of weeks. So today got stumpy out only to discover front suss had lost all it's air! I pumped it up and went for a ride again. They again performed well and didn't deflate. I am confused , could I have a slow leak?

[snotrag]

Sounds like the Valve may have stuck perhaps?

Is it a Fox Float Im guessing? The little recess that the valve sits in can fill up with crud, suggest you let the air out, remove the valve core and give them a good clean in that area.