Chickens, even young pullets, aren't surprised by an egg coming out that finds them standing in the wrong spot with no time to reach a nest. If anything, it's the opposite - they spend a
long time before the egg comes out, getting ready or pacing or yelling or acting anxious/nervous. So it's not that it found her in the wrong spot and she just dropped it there. She's just inexperienced and trying to find a suitable spot to make a nest. What we build for them and is obvious to us as the right place to lay, isn't always so obvious to them - sometimes they have other design preferences

What I have found is that they like to rearrange the nest before settling in it. They'll pick up pieces of the material and move them around, fling them behind their backs, pull them closer, etc. So a bedding material that has discernible pieces to be picked up and rearranged would be better. That means sand or fake grass pads may not be ideal (personally I'd never heard of sand used as a nest material). What I have in my nests is hay, and it works great. The strands are long and intertwined so the material holds together and isn't easily kicked/spilled out like shavings are. And hay isn't hollow tubes like straw is, so less risk of mites finding hidey spots in the hollow spaces.