While it would be very unlikely for you to get pregnant under those circumstances that you have described above, it is a possibility. The reason for this is that sperm can survive for up to 5 days outside of the male reproductive tract, meaning that there was obviously still some time that they would have been alive and functioning, and likely a few surviving sperm in your vagina and reproductive tract as well. Intra Uterine Devices are highly effective at preventing pregnancy when used correctly, and have one of the lowest failure rates of any contraceptive available.
It is believed that they work mainly by causing inflammation of the uterus, which makes for a hostile environment for egg and sperm, although there are models available that will also utilize hormones as well, and the basic copper model does have some spermicidal activity. As soon as the device is removed, the inflammation will begin to resolve and the uterus will become more hospitable for a fertilized egg. If the timing was just exactly perfect, a fertilized egg could arrive and be able to survive, which could lead to a pregnancy. Please speak to your OB/GYN or primary care doctor
if you believe you may be pregnant to answer your questions and begin pre-natal care. Also, avoid all alcohol, tobacco, and other drugs if you may become pregnant.