On a joint checking account can the trustee of a Trust demand any money taken to be returned to that account?

I am afraid you have not provided enough information to answer this question definitively.  In general, placing two names on a checking account means that each person owns the account and can take money from the account.  Even if the person who withdrew funds was supposed to leave those funds or use them for the other person's benefit, this would be difficult to prove.  If the person who withdrew the money was supposed to leave it, the Trustee can demand that it be returned but I doubt she or he could enforce that demand.