The chances are very close to 0. The amount of calculations needed for this is incredibly large. Suppose you already know the set of 12 words, but not their order. The number of possible permutations is 12! (12 factorial), which is 479001600. But there are much more words used for seeds. A meager set of 100 gives the number of permutations of about 9E157 (9 with 157 zeroes), and only millions of them correspond to existing wallets.