Per some internet research, disposable diapers contain superabsorbent polymer (SAP), cellulose pulp, and an adhesive to hold the diaper layers together. They can also contain fragrance, lotion, or essential oils.
I'm thinking the SAP would have all changed to gel in the washer and will likely wash out with several washings. Same with the cellulose. I'm not sure about the adhesive, but the lotion and fragrance/oils might be "stickier". I'd remove the disposable bits, then wash the diapers on hot several more times with extra rinses thrown in, turning them inside out to wash at least once. If you have repelling issues after that, you'd probably need to strip. If not, I'd think they'd be fine. If all else fails, ask your MIL to buy you new dipes!

Just did a little more research. From what I can find, the adhesives used in disposable diapers melt at around 180 degrees. Not sure how hot your water is, but if it's above that temperature, my concern would be that the adhesive could have melted, then set in your diapers as it cooled. I'd wash AND rinse on hot water several times to try to get as much of it out as possible.
You could also contact the manufacturer, both of your BGs and the disposable diaper, to see what they recommend.
The plus side is it was only one disposable. Probably the chemicals were pretty diluted in a full load (I'm assuming) of diapers.
Hope it works out for you!