A couple of issues. First, I am limited generally to commenting on Massachusetts law. If you daughter lives out of state, the adoption laws in that state obviously matter. That being said, in MA, if a child has not reached 18, a parent must generally be provided notice before the child can be adopted. If the child is over the age of 18, parental notice/consent generally isn't required. I really can't speak for other states, however.
A starting point would be to call the local court with jurisdiction over adoption matters in the state/county where your former wife lives. Ask them if adoption records are public in that state (sort of unlikely), and if not, which individuals have standing to review confidential adoption records (e.g. does the biological parent of an adopted child have the right to review the adoption records?). Then ask if you would/should have received notice in MA if your daughter had been adopted in that state. Then ask if you would/should receive notice if an adult child of yours was adopted by someone. Once you know the rules, you will probably figure out the next step.
Ultimately, you could file a Modification to seeking a change in child support if you really felt this was a strong possibility, but it sounds a little like a shot in the dark. It is fairly uncommon for step parents to adopt when doing so would jeopardize child support from the biological parent.