suspicious persons

ok....so many of you kids are probably really smart and comfortable here in japan by now.... well, most days i'm not. i've been here about 7 months and only have a basic grasp of the japanese language. hence little things happen all the time that make me realize just what a clueless gaijin i am....and i am going to share one of these moments (a rather large important one) with you in hopes that no one else will fall prey to the same thing i did:

some guy came to the door and said he was a policeman and needed our information (phone numbers, places of work, birthdays, etc) for the city police records. he also asked to see our gaijin cards. i was instantly suspicious because his uniform didn't look very policey, plus he didn't seem very confident, and i just had a bad feeling. my boyfriend assured me that the guy seemed nice enough & he was probably collecting our info for emergency evacuation procedures or something and persuaded me to give the guy my info (what a sweet trusting lad he is! and i always overreact, so i followed his instinct on this one). anyway, i asked my boss about it, and she said it sounded strange, so she called the police and asked them about it. of course they hadn't sent anyone out and said that it must have been someone posing as an officer to gather personal information about residents in order to: 1)scope out the place for anything worth stealing and find out who works outside the home and what times 2)steal identity numbers to make fake IDs and/or take out loans with someone else's ID number & other info 3)who knows what other creepiness??

so what i would like to share with you (besides my own stupidity at giving him ALL my personal info!!) is what the police department told my boss:
1) the police department usually sends officers out in pairs, not alone, to someone's door
2) if the police want to collect personal info, they will tell you explicitly what it's for (and this would be a very rare case). if language is an issue, they would encourage you to call a japanese speaking friend or would just leave and return later with an (insert your language here) speaker
3) police officers will always show clear IDs, and you can copy down their ID numbers for your records
4) police officers who come to your door will always be wearing large badges, also with ID numbers
5) and of course the usual....always keep your door locked, hide your valuables, don't answer the door to anyone you don't know, blah, blah, blah.

so i hope someone out there might find this info helpful!! now, i have some questions. has this happened to anyone else? anyone else heard something about people doing stuff like this? if so, any advice on what extra precautions i should take? (i.e., can i change my ID number or something like that?) any tips on dealing with charges you didn't make in japan (in case it comes to that)? thanks! :) and ganbatte!!