I don't think we lose "skill", but we lose what I'm going to refer to as "protocols".
For example: if you've been playing everyday for a while you have protocols for every bit of replaymaking that you did in that period. Take boomhits for instance. If all you've been doing is boomhits for a substantial amount of time, you have a protocol to get those big booms easily. This protocol was subconciously made, and executed when it was needed.
When you leave you forget these protocols and when you come back you start forming these protocols again.
"But fudgie..." I hear you say. "Sometimes I spend hours on getting this one boomhit, while the day before I was done in 10 minutes."
This is probably because you were in a completely different position the day before, and already had a protocol established for it. By spending hours on this boomhit in a position you are making a more refined protocol, for all sorts of booms.
In this example we also see protocols aren't always useful and need refining, so sometimes when you leave for a while and come back you can make a better protocol.
This could also explain why I'm suddenly shit at -9.82 when I did mostly -30 for a week or two.
But hey, that's just a theory. A TORIBASH theory. Thanks for reading.