Thomas, You can play in medal and stableford competitions simply to get your three cards in, as long as they are qualifying competitions. Of course you can't win. As soon as you have entered your third card you are once again active. But you have a handicap committee. They have the power to reinstate you at your old handicap if they want, just as they can adjust handicaps at the end of the season.
My younger son's handicap of 9 lapsed, largely because he works Monday-Friday and plays football on a Saturday. But he's able and welcome to play in Sunday social events in which it doesn't matter if his handicap is active or inactive. The majority of those playing in these social events only play social golf and don't bother to maintain a handicap.
I have only ever been asked to produce a handicap certificate in Denmark and Holland. I don't have one - I don't need it at my own club where the computer recognises my membership card. Royal Liverpool, Formby, Royal Birkdale, Royal County Down, Wentworth, Swinley and many others I've played as a single player without even proof of membership of a club.
We have a reciprocal scheme with a number of clubs in the midlands and north west and none of those has ever asked for proof of membership when I claim my 50% green fee. I am always made most welcome.