I think Scott was probably at home on the Friday night because police examined Bee's phone records so they would have examined them all. He could have left his phone at home but that doesn't seem to have been one of his tricks in his many subsequent journeys.
Thinking it through, he doesn't seem to have been worried about leaving Bee's body at the location he went to, for quite a significant period of time. If it was me I'd be thinking what if she's discovered by humans, and what if she's discovered by foxes, before I get back to bury her, especially at that time of year when temperatures are going to make the body smell quicker. I've only got to bury a few vegetable scraps at the end of my garden and foxes are digging them back up the next night, their sense of smell is acute. But we're talking about an unburied body, most likely. The fact he was out with Sarah setting false trails with Bee's phone that afternoon/evening shows how comfortable he was that Bee's body was secure and would not have been moved before he would return to it over 12 hours later. So what would make him feel that secure? A suitcase or a roll of carpet or tarp is going to be more visible and could draw attention so I think he wouldn't feel so secure that her body definitely wouldn't be discovered. Plus he's got the problem of actually being seen in broad daylight at lunchtime putting it there and she's going to be heavy to move from the car, so I don't think she'd be that far from where he could park his car. I also don't think it would be a place frequented by motorists such as a lay-by, so it needs parking but in a less used area. It's a really big thing to leave a dead body somewhere, I think it helps to try to put oneself in that kind of mindset, being caught before they've finished their staging, soon after he was last known to be with her, it was really high stakes that she not be discovered miles away in the opposite area to where they were setting a trail for her phone.
I think he knows an abandoned building and his stop off at the lockup before he picked up Bee on Saturday morning could have been to get tools for breaking a lock and securing it again. Somewhere he could park up close and not be seen by passing traffic. Somewhere that he knew of before he set out, so he wasn't using that trip to scout around.
There are other possibilities like dumping a suitcase temporarily in water, it's not going to really drift, but again I think he'd have worried about being seen and it would most likely need to be close to the road. I prefer a more secure building, or shed location. Perhaps even public toilets with parking that were locked during lockdown.
MOO