The baby Amber Davis had been looking after for six months had been placed with her "new family", so Davis was packing up her things when her son Josiah asked why she was doing so.
"I realised I had a responsibility to try to help my growing, curious four-year-old grasp something that I still don't quite understand myself: why can't she stay," Davis explained in a Facebook post shared by Love What Matters on 6 May.
"As I fumbled my way through an explanation about needing to go live and be together with her sisters, I could see the look of confusion on his face... 'but we're her brothers'.
"My brain scrambled for another answer, but I blanked."
Davis attempted to change the subject by explaining to Josiah that she was pregnant and his baby sister Avonlea would be born soon.
"I could tell by the look on his face that my lame attempt at explaining things had failed to add up," she wrote.
"It just doesn't make sense. Not to him and... frankly... not to me, either.
"The heartbreak is overwhelming me tonight. The tears just won't stop. This first loss is more painful than I ever imagined it would be and something I wouldn't wish on my worst enemy."
Davis then explained how the gut-wrenching emotions she has experienced have made her feel about her future as a foster carer.
"The next time I see that all-too-familiar phone number pop up on my caller ID, asking if we are willing and able to open up our hearts and take in another child who needs us to sacrifice everything we have in order to love them for an undetermined amount of time, I already know what my answer will be.
"Absolutely. Let's do this. For six months or for forever... we're in."
A spokesperson from The Fostering Network told HuffPost that Davis' decision to share her experience could be a big help to her and to others going through similar things.
"Whatever the reason a child moves on, foster carers will experience a range of emotions when a child leaves their home," they explained. "Sadness to see them go will often be mixed with happiness to see them move on to a more permanent situation.
"Being open about these feelings and discussing them with family, other foster carers and their supervising social worker is important, as is preparing any birth children for the emotions they might feel when they say goodbye to a child they have shared their lives and homes with.
"The Fostering Network believes that fostered children should be able to stay in touch with their former foster carers when they move on and, through our Keep Connected campaign. We are campaigning to ensure that all children are enabled to do so where this is in their best interests."