1) What kind of "paper" was signed? (ie: a letter, a notarized letter, a custody agreement, etc.)
2) Was grandma granted legal guardianship? If so, check out the laws regarding this in your state. In some states, legal guardianship can be revoked by a parent.
3) Did "dad" Voluntarily Relinquish his parental rights? If so, there's no going back. This is a permanent done-deal.
If I were you, I would try to speak with grandma (if appropriate) and find out her position on the custody matter -- Is she willing to consider granting dad custody (if it's not #3)? (Also, where is the mom???)
I'd find out (and obtain a copy, which dad SHOULD HAVE, of) what kind of papers were "signed" giving grandma custody and rights to decision-making on the child's behalf. Then if your situation is #1 or #2, I would pursue custody through the Courthouse. But be prepared to show good reason why dad couldn't raise this child last year, and why he's "all of a sudden interested"-- ie: how he's going to support and take care of this child until she's 18.
Personally, I believe that people's situations do change over time, and maybe your husband wasn't ready to be a father (for whatever reason) last year. However, I also wonder if father has had visitation with his daughter over this period of time; and if he hasn't, if pursuing custody at this time would be more detrimental to her well-being.
If he hasn't seen her or had consistent contact with her, he might just leave well enough alone, so as not to disrupt her and cause adjustment problems. (I don't know how old this child is, either).
