Heartbroken

This isn't my usual adventure story and so far it doesn't have a happy ending.
About a year ago my parent finally put our old homestead on the market. This was a big step for my mother who has such fond memories of their home. Her babies learned to climb those stairs.... It was a big deal for them to not only admit that they needed to live in a smaller, one story home, but to actually put their house on the market and plan for moving.
We all put a lot of effort into fixing up the place and it really looks nice. The whole house was repainted, the kitchen was renovated.... We weren't unrealistic. We know the market and we knew it was going to be hard to sell, but we were still hopeful. Then the long wait began. The house sat and sat on the market an no one came through it.
It had been up for nearly a year when the realator finally called with someone who wanted to go through. A bid came in, it was a bit lower than they had hoped for, but my parents accepted. The buyer was preapproved for a loan and we thought things were perfect. My parents had been shopping for houses this whole time, and they with the house sold, they were finally able to afford one they really loved. It was perfect. The floor plan matched their ideal layout. The basement was huge. It had tons of storage, a larger kitchen, a resonable sized yard. My father has been through many surguries in the past few years, so purchasing a single story home with a walk in shower was just what they dreamed of.
My mother and I began shopping for paint samples, furniture and browsing interior design books. It was hard to get them motivated, but my husband and I had spent a few weekends helping my parents pack. Since the buyer was going FHA, we had also been subjected to several inspections and had to make a few repairs. My parents had paid for inspections on the new place too.

All of these dreams came abruptly to a halt last night when we learned that the buyer of our old house had been denied her loan. This is three days from the expected closing date. How can this happen? She had had a preapproval letter when she placed the bid, so I don't really understand how this could happen. And if it can happen, why weren't my parent notified at some point that things might be iffy? I feel bad for the people my parents were buying from too, but mostly my heart is broken for my folks. They are good, honest people who deserve a nice place.
I know we've taken a lot from them in the past and especially this year since things have been really tight with us, but I wish I had everything I owe them. It still wouldn't be enough, but it would be a step closer. Mostly, I just wish there were someway I could make it everything right.
Sigh.