Hello, I'm Dr. Deb.
I recently came online and see that your question about Mira hasn't been answered. I'm so sorry that you've had to wait for a response (especially under the circumstances), but if you still need assistance, I'd like to help if I can.
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Believe it or not, this sort of thing happens much more frequently than you might realize. In the majority (if not all of the cases), the pup will be fine. Even though she has a cleft palate, the nipple remnant isn't likely to become lodged there if this was your concern. And, since you don't see it in her mouth, it's more than l likely in her stomach or possibly in her intestines by now.
She's not likely to become obstructed with this object; she should pass it in her stool between 12-24 hours although it may take longer if it remains in her stomach before moving on.
I'd monitor her stools over the next few days for evidence of it.
I wouldn't change your feeding regimen but continue feeding her as you are currently doing but refrain from use of a nipple on the syringe (which is probably your plan anyway). Pups can be weaned around 3-4 weeks of age so you might see if she'll eat on her own.
I hope this helps to reassure you, however belatedly the reply; once again, my profuse apologies for that. Deb