I sometimes wonder if people are concerned about text messages they send to me (although I refrain from communicating that way with clients). I am also aware that people who are having an extramarital affair worry about text messages being retrieved via subpoena.
Through research I found that Verizon keeps and make available basic text message details for 90 days. This includes who sent the message, who it was sent to, the date, and the time. No information is kept beyond that. Verizon texting records which include "content", i.e. the actual conversation, are only available for about 10 days before that information is written over and lost forever, even with a court order. Verizon does not save your texts, they simply deliver them. Other carriers have similar policies.
Most cell phones store messages and pictures until someone "cleans" or deletes items on the phone, or the phone deletes information automatically to make room to store new messages or pictures.
If you snoop around your spouse's phone, unless you legally own the phone, share it with your spouse, or he or she lets you look at it, you may open yourself up to a civil suit for invasion of privacy and may have to pay money damages if you look at messages or pictures on it.
Another option is digital forensics. Here, someone who is highly trained in digital technology can retrieve text messages and images from the phone even if they've been deleted. Again, to make sure you avoid legal problems with privacy laws, you must be the owner of the cell phone to do this. lso keep in mind that it may be expensive to have the phone examined by a forensic specialist.
Finally, be aware that it’s possible to set up text message forwarding on a cell phone. For instance, with IPhones, text messages can be forwarded to an IPad. Google Voice is an app that allows you to forward text messages to another phone. If you are worried, check your phone for any features that may have been set up to allow text forwarding.