Baking – What caused the crust on on the top of the bread to separate from the rest of the loaf

There are some previous questions with good answers like this one, or this that go into much more detail than I'm about to.

You said your bread didn't rise with the first rise, if you don't have a first rise you can't go onto the next step. If your yeast was old, or the temperature was cold in your kitchen or you used cold water in the dough, or the yeast came in contact with salt then its action could have been slowed down drastically and it would take much longer to get a rise. I've had a first rise take up to 4 hours in the past because of these factors. The times given in recipes are just guidelines, you have to be result-driven. Active dry yeast also takes longer than quick yeast to activate. When using active dry instead of quick yeast you would get better results by mixing it with the water before mixing in. I'd recommend using quick yeast as it's milled into smaller grains and you can mix it directly into the flour.

Of course your yeast may have simply been dead, or killed by salt or heat. Get some good fresh yeast and store it in the fridge to keep it fresh long-term.

Also, using all whole wheat flour isn't going to produce anything like a baguette. Whole wheat flour is very heavy compared to white flour and will take longer to rise. A half and half mix would work better. I'd recommend sticking to the recipe first, then gradually modifying it over time until you get your desired result.

If bread falls after you score it, it's because the bread is overproofed. Basically, the bubbles of carbon dioxide have reached the largest size that the structure of the dough can support and the stress of scoring causes it to collapse. They key is to either score it earlier and let it continue rising a bit, or to score & bake it earlier (this works great if you have a very hot oven and can find a way to get some steam into it).

If your neighbor came over with bread and it flattened in your oven, it's possible that hers also overproofed in the time it took to transport it (or the extra jostling of transportation caused them to fall).