MIBG has always produced the most worry in our family. While it can be fairly easy to spot disease in the extremeties, for me, it is far more difficult to separate areas of disease from normal areas of uptake in the abdomen and chest. I am sure you already know but there are several organs that show up in the scan. One in the chest is the heart. If your daughter has a port or was wearing the same clothes as she had during the injection, I have also seen those spots show up as well. I will never forget seeing a huge spot light up on my daughters arm. The day before the IV had leaked onto her blanket. During the scan the blanket was laying on her arm. It took us a bit and a reposition but we eventually figured it out. Without having a good idea of what you saw it is difficult to know if something like that would be reasonable. At our hospital, if something was seen by the radiologist we would know something almost immediately regardless of our appointment. Honestly, if I ever think I see something I always email my oncologist and let her know what I saw. This also usually helps me to get the answers (or relief) more quickly. Look at it this way, if it is disease, you want it dealt with quickly. You don't want to wait for weeks to treat it. In that case, contact your oncologist and let them know you saw something and you are concerned. More than likely they will be willing to take a look at it for you.
I know it is a scary time. I despise scan week. However, it is not always bad news. I wish you the best.