This is a tangent but there are other, arguably better ways to give the user confidence the order took place in your example. You could show the line items to t

This is a tangent but there are other, arguably better ways to give the user confidence the order took place in your example. You could show the line items to them again with some indicators of completion, or show the order added to an excerpt of their order history, where perhaps they can tap/click to view line items. Something like that is a bit more convincing than just thank-you text even with the delay, IMO, though it may be tougher to pull off design-wise.