Was there only an order to have the type and screen for on call to OR, or was there an actual transfusion order? I dont know your facilities policies but at mine, we have 30 min to initiate the transfusion from when the blood was verified and picked up from the blood bank. In my opinion, the person who signed for the blood from the blood bank dropped the ball. Who did they give it too? There are so many variables and steps to follow to ensure safe administration of the blood should not have just been causally set somewhere, and when said person received it they are assuming responsibility for the unit. That responsibility is to get the unit to the person in care of the patient or an acceptable and appropriate person, ie the charge nurse. This is no way should be placed on you for blame as you never received and therefore accepted responsiblity for the unit dispensed for your patient.
I agree that the blood bank should of been informed of the unit not being needed at that time, but who's to say the unit wasn't already in route or in the OR when the doc determined it was no longer necessary. And if it was picked up after deemed unnecessary, was it brought to the OR with the patient still in the OR or PACU? Or when the patient was recovered and brought to the floor? Why did said pick up person not find where the patient was to bring the blood to their location, ie... if the patient was in the OR and it was brought to the unit or vice versa? What the PACU charge the same charge you told about the request to have the blood brought to the unit? If so, this person would have received report when the patient arrived in the PACU, and your informing it was no longer needed, to me in this scenario, makes sense and should not have warranted further explanation on your part.
Why was the blood not returned until 5pm the following day? Did the room not get cleaned until then? Did the person that found the blood hold on to it for some reason before returning it? Or was it not found until that time, again demonstrating the lack of communication and responsibility of the person that picked it up to begin with?
I would not stand for this getting pinned on you, the only thing that you may hold some responsibility for, is possible communicating to the blood bank when the blood was not warranted any longer.
You are a new nurse with 1 month solo after a 2 month orientation ( 2 months really?? That seems way to short, especially for such a specialized area, but that's a different issue in itself) you communicated with your charge, who also did not follow up in this situation.
IMO, you are not to blame in this, and if it were me I would be damned if it would be made out to be my fault.
Sounds like someone is throwing darts blind and you took the hit. I hope the investigation proves your role in this and clears you of any fault in this situation.
Keep us updated if you dont mind, I'm curious how this is going to end. Good luck