FYI, it used to be that you could register your pet's microchip yourself - I did with all my dogs except the last adoptee.
However, it seems to have changed, probably with the new TschV law in Sept 2008 - at least, the muttley I adopted in early 2009 was the first where I could not register my dog myself.
(Odd, since mandatory microchipping of dogs came into effect in 2006 - and I registered 2 dogs myself after that date...)
Anyway, it might be a good idea to check the ANIS database every so often; I logged in once and found my info pretty badly screwed up. Seems there had been a recent software update - a quick phone call sorted it out.
Also, be aware that microchips can travel - you should have your pet scanned every once in a while just to make sure that the chip is where you expect it to be, and that it is indeed still working.
In addition to wearing tags with my phone number, mine also wear tags that say they are chipped. (As well as their medical tags... paranoid? Moi?

) Hopefully anyone scanning them will be persistent if the chip is not found initially. Not such an issue with dogs, as everyone expects a dog to be chipped as per law - but with cats this could be a problem if the scanner only checks the neck and then gives up.
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We're still keeping our paws crossed that Maud makes it home soon.