(NIV) Genesis 14.13 - A man who had escaped came and reported this to Abram the Hebrew.  Now Abram was living near the great trees of Mamre the Amorite, a brother of Eshkol and Aner, all of whom were allied with Abram.

Now that Abram knows, it will be up to him to decide how he will handle this news.  Depending on how Abram felt he should handle this situation would warrant his response.  How he could handle it as well would be the issue.  Getting those that captured him to hand him over could be the biggest obstacle if he does decide to help.  If he will help the others that were captured as well is also an interesting question.