I don't know if I'm off topic, but I read somewhere (can't remember the article) that approximately the number of possible private keys is similar to the numer of atoms in the universe, and running a computer capable of cracking a private key would require the energy produced by a star...obviously there is always luck, but seems unlikely
As another poster has already noted, searching for the private key to a given address is different from encountering a collision between two random addresses which is much more likely due to the birthday paradox. However, the probability that such a collision happens, is being noticed, and leads to undesired transfer of bitcoins is extremely small.
Onkel Paul