When a crease is visible in a scan like that, there's a near-100% chance it's actually there :-)
It may not show well while "in" fluid (if it's well-pressed as it appears,) but the damaged fibers in that bottom stamp appear to span the entire width. Those should "flash" white shortly after being removed from fluid.
Are you using Clarity by any chance? That dries way too quickly for my liking, and could make it much more difficult to detect a fault like this. Ronsonol should show it for at least several seconds while drying, probably longer.
Sorry to say, but there is a definite crease on the bottom stamp at the bottom of the design. This would be considered a damaged pair to most collectors! Hope you did not pay very much for it. Margin about normal.
What there is is a line that has the appearance of a crease in this image. Since it does not show up in fluid, it might be a flash crease, but they are not usually visible to the naked eye until after you know it's there. It still might be a natural flaw in the paper which does not involve any paper loss or damage. There is no way to tell without a direct examination.
Notice the crease at top is much wider and has a wrinkled appearance throughout. It's obvious in several places that the paper was clearly bent. The right margin and numerals show this very clearly. But the line on the bottom is very thin and has a smooth surface without any of the wrinkling that is visible on the edges of the crease above. It still might be a crease, but there is definite reason to think that it might not be.
A flash crease is one that is invisible to the naked eye or when dipped in fluid, but will show up as the fluid dries when the stamp is held at an oblique angle under a light. The stamp itself dries a bit faster than the crease does, so when it is almost dry the crease "flashes", that is to say a dark line becomes visible where the crease is. Flash creases usually happen when a creases stamp has been ironed, something that clearly has not happened here or the top crease would not be so obvious.