I couldn't get ahold of X.
This construction is commonly used in informal speech in the US. I have heard it used by well-educated people (native speakers) of both rural and urban background, in both the Mid-west (Michigan and Ohio) and the Northeast, contrary to the comment by Michael Harvey.
This phrase means "I tried to make contact with X, but was unable to do so. It does not specify whether the method was telephone, text, email, postal mail, or personal visit, nor in what way the attempt failed. It merely says that the attempt was made did not succeed. Often additional statements will clarify how and when the attempt was made and how it failed.
I have also heard "get hold of" with exactly the same meaning. "Get in touch with" also carries exactly the same meaning, and I don't think either one is particularly preferred to the other -- both are informal. The choice is a matter of personal style. Any native speak will understand any of these choices and attach the same meaning to them.