[1] After walking around the city all day to attend meetings, you take your shoes off in the unknown person's office which you happen to be borrowing for the afternoon. After sneaking in 20 wonderful minutes of shoelessness, you put on the extra pair of more comfortable shoes which you stashed in your purse for this purpose.
[2] In all of the newfound comfort, you forget all about pair #1, including when it comes time to bring them home with you.
[3] Two days later you realize you left your shoes in someone's office. Oops. You go searching for them, only to find they have disappeared.
[4] You ask the cleaning lady on the twelfth floor (i.e. scene of the crime) if she knows what might have happened to your shoes. She confesses to seeing them yesterday. She doesn't know where they are now, though. She advises you to speak to the men at the security station on the second floor.
[5] You visit the second floor and ask the security men if a pair of shoes have turned up in the lost and found. What a strange thing to lose, they comment. Yes it is, you agree. They ask what the shoes look like, and you explain that they are black and have high heels and are actually pretty cute. A quick search determines that these men don't have them, but they will give you a call in case a pair of shoes fitting your description surfaces.
[6] You thank them and secretly hope the shoes will turn up. After all, the security men did find your building badge which you accidentally lost last week.
The end.