I think the problem with no stock is that it was all bought up and we don't have enough to replace it. No one has large volumes of toilet paper sitting in warehouses, because why would you ever pay to do that when you can just make more on demand? TP manufactures crank it out 24/7, and people buy it 24/7, and the stock remains relatively stable. Manufacturing is adjusted to meet demand, and just runs in equilibrium producing it as needed, and by this point they know what production capacity is needed to supply the population. All stores we all shop at likely gets at least 2-3 shipments of goods in per week, including toilet paper, but they never get their entire inventory worth of toilet paper, they are likely getting a few days to one week's worth of TP, which is just enough to replace what is normally bought because it is produced at the same rate it is consumed. So when there is a panic and small portion of the population buys the entire available supply of TP, it's going to take awhile to fully restock it. If the store shelves held a 1 month supply of TP, it would take a month of production to replace all the TP (and that's if no one continues buying it). If the store shelves hold a 2 month supply then it will take 2 months, etc. I have no idea what the baseline amount of TP on store shelves is though (whether it's a week, a month, 3 months, etc), but it's going to take at least that long to fully restock it.
I still don't understand the initial run on TP, but I do understand how panic buying begot more panic buying, and as I've recently stated, I wish I would have gotten in on the ground floor of that panic buying and bought more TP the last time I saw it available, because I am starting to get low. Not desperately low, but enough that it has me concerned. What if I don't see any in my next 2 weekly shopping trips? Do I take off work and risk getting/spreading infection by going to all the local stores trying to find TP? Or will I just adopt this strategy?:

Anyway, after really thinking it through it makes perfect sense why there is still a shortage of TP. It's being bought up at
at least the normal rate, which probably matches our capacity to produce it, thus empty shelves remain empty. Due to the initial hoarding I suspect TP is still high in demand and is actually getting purchased (or would be if it was available) at a higher rate than normal demand.