
As fars as I know, your girl wouldn't have the clear/opaque discharge with a phantom ~ I know one of mine, had a fantastic phantom, every sign that she was in pup except she didn't have any discharge.
I personally think 24 days is too early to see anything on a scan as the whelps will have only just attached themselves. I'm told by the lady who scans for me (& my Vet agrees) that the best time to scan is between 30 & 35 days. You don't actually see that much, just a blob & if it's a good scanning machine you might see the heartbeat :)
Where abouts do you live? I would want a scanner that knew what they were looking for & in my experience, most Vets are pretty useless at scanning & if you're lucky most will admit to this ;)