SCREENSHOT GUIDES
What if your Mac screenshot preview disappears too quickly?
A dismissed preview does not mean a lost screenshot. Find the file or keep it close for longer.
Find the screenshot first
The system thumbnail appears briefly. If you leave it alone, the screenshot is saved to the configured location. Open that folder to find it after the preview disappears. Press ⇧⌘5 and check the save location in Options.
Keep it in a bubble for later
Launch SnipPop, check the screenshot folder, and grant access if prompted. Capture as usual. Unpinned bubbles dismiss after five idle minutes, with up to fourteen at once. Hovering, editing, or dragging pauses the timer. Pin an image to keep it around.
What if no bubble appears?
Check that SnipPop is running, bubbles are not hidden, and screenshots save to a folder rather than only to the clipboard. SnipPop also needs access to that folder. Dismissing a bubble does not delete the original file.
Reference：Apple: Take a screenshot on Mac