First of all, condolences for the recent loss of your husband, I know this may be a difficult time for you.
When you say the annuity was purchased using IRA funds (from AARP) and you "put the annuity under the Trust", exactly what do you mean (if you know)?
Do you mean that the Trust was the owner of the Annuity, or the Trust was the beneficiary and/or your husband was the Annuitant?
If the check was made out to the Trust, it seems that the Trust was at least the beneficiary.
Do you know what the original purchase amount of the annuity was and was the Trust receiving payments from the annuity while your husband was alive?
Unfortunately what you can do and can't do depends upon exactly what happened from the time the money came out of the AARP IRA until you received it as the result of your husband's death.
Unless you already have the information, you will need determine when and what the status was of the origin of the annuity. Do you know what tax year that the annuity was purchased? It seems that it may have been this year as you were asking if the funds could be returned to the IRA? Once the funds were deposited into the annuity, unless that annuity was part of the AARP IRA (I presume that was your husband's IRA?), you would not be able to redeposit the funds in the IRA. You may be able to roll the funds over to another annuity, but that depends upon the timing and the ownership questions I and Trust status I asked about previously.
What was the date that you received the check for $30,000. payable to the Trust and have you deposited it into a Trust account?
Was the Trust a Joint Revocable Living Trust or was it just your husband's Revocable Living Trust; I realize the Trust was using his Social Security Number.
I apologize, but what seems straightforward, quickly gets complicated when dealing with IRAs and Annuities.