From News-Gazette.com: City Attorney Fred Stavins said that, even if they are public records, deleted text messages are impossible to recover, and the city's legal department provided The News-Gazette with its research to prove it.
In December 2012, city officials called around to various cellphone providers to determine how long those records are retained in the cell company's files.
[. . .]
AT&T: No records are kept of customers' text messages — that data can only be accessed on a customer's phone.