In fact, 99.999999% is an extremely low estimate. The number of ways that a deck of cards can be shuffled is 52! Which is equal to 8065817517094387857166063685640376697528950544088327782400000000000 possibilities.
If you shuffled cards every second from the birth of the universe until now, you still wouldn’t even come close (statistically) to getting the same arrangement twice.
For generating unique IDs, you can combine a random part with some other data, like the current time, so if it’s only those that are generated within the same millisecond that you even need to worry about.