I'm curious to know what happened.
I'm kind of, but not really, in a similar situation.
I delivered a baby girl at 23.5 weeks almost 6 weeks ago. She was born alive and died in my arms. The labour had been brought on by a bacterial infection in my trans vaginal stitches. It made my uterus irritable, and started contractions, which dilated my cervix, which allowed the infection to ascend to the bottom of the gestational sac, which burst when the infection touched it, which then infected the entire amniotic sac as well as the placenta and my daughter...
My antibiotics were discontinued 4 hours after delivery. I asked about residual infections and was told everything would have come out with the afterbirth. I went to a Dr 48 hours later, feeling like crap. Was told it was normal post partum pain. Went to another Dr 6 days after I delivered, still feeling like crap. Asked about infections, was told it was unlikely, and was sent away. Saw my OB (who'd been on vacation the entire time), on August 19, so 12 days after delivery. She didn't want to look yet because it hadn't been 6 weeks. I went back a couple of days later, still feeling like crap (tender abdomen, painful cramps, bachache, chills, odd bleeding), and she looked, and yep, uterine infection.
I did IV antibiotics for 4 days. In that time, I never started to feel better. I actually got worse, to the point where I couldn't sit cuz everything was getting squished up, couldn't wear regular clothes as the pressure on my stomach was unbearable... I saw a Dr 24 hours after starting antibiotics. Was sent home and told I needed to give them more time to work. Saw a Dr 48 hours after starting. Sent home told I needed to give the meds more time to work. Went to an ER that night. Kept for observation but told I really just needed to give the antibiotics time to work. Finished antibiotics on a Saturday, had an ultrasound to see about retained tissue on the Monday. Nothing was found. Saw my OB on Tuesday. She booked me for an emergency D&C for the next day and gave me more IV antibiotics so I didn't get septic overnight.
Had the D&C Sept 1st. She found 2 plum sized blood clots blocking my cervix as well as alot of infected mucous. She cleaned me out. I went pee after surgery and another lime sized clot came out.
My infection has cleared up since then, although I still don't feel 100%. I am still bleeding, and have been almost every day since the surgery. Pathology has come back on the stuff she removed, and she did find retained deciduous tissue (the tissue that connected the placenta to the uterus), and it had become necrotic.
I have now been identified as having a dysfunctional uterus, which is why I am still bleeding. Apparently my hormones are so confused because I was pregnant, delivered without being ready to and without building up the labour and delivery hormones, then I had a significant drop in hormones, but that deciduous tissue kept secreting a small amount of pregnancy hormones, so that has confused my body. And now I have to take Estrogen pills to try to stabalize my hormone levels.
So there you are. There was retained products even though they didn't show up on the ultrasound. They had collected behind the cervix and weren't visible as they weren't 'floating.'
It isn't rare to retain products. I have lost 6 babies now, all at various gestations. With 2 prior ones (an 11 week and a 13.5 week), I had MMC, and needed the D&C. With the 11 weeker, I was hemmoraging and they thought everything had come out, but I wouldn't stop bleeding. Ultrasound showed a small amount of retained tissue... Yeah, try everything was retained! With the 13.5 weeker, I had a D&E before bleeding started. Five days later ended up back in the ER hemmoraging. Ultrasound showed a small amount of retained amniotic fluid... Yeah, try everything was retained because the surgeon messed up!!
You don't always need to be bleeding excessively though to have retained products. Thats why no one investigated me sooner after delivering Devon. I wasn't bleeding excessively and I didn't have a nasty odor coming from down there... Obviously I did retain stuff though. Bleeding and odour aren't the only indicators. Make sure they listen to you.