Quick answer
The short version
Search the strongest clue you have, then narrow with a second one. Text first if you remember any. Otherwise subject, then period, then look, then the work it belonged to.
01 · Method 01
Search text you remember.
If the screenshot contains text, and most do, search the phrase, product name, error message or sentence you remember. Text recognition makes the inside of an image searchable, which is the difference between scrolling and finding.
Search a distinctive fragment rather than a full sentence. Recognition is rarely perfect on small or stylised type, and short queries survive imperfect recognition better.
02 · Method 02
Narrow by time.
You may not remember the date. You usually remember a period: last summer, during a project, before a trip, around a launch.
Sorting by date and jumping to that period is often faster than a query, because screenshots arrive in clusters. Land near the right week and the surrounding images tell you whether you're close.
03 · Method 03
Search the subject.
Instead of trying to remember exact text, describe what the screenshot was about: “fintech dashboard”, “pricing page”, “authentication error”, “editorial typography”.
This only works if something in your system understands subjects rather than strings. Where it does, it's usually the fastest route, because a subject is what your memory actually stored.
04 · Method 04
Use visual clues.
Ask what you can still picture. Dark background? An orange accent? Large serif type? A chart? A phone interface? Visual memory is often more intact than verbal memory, and it's the clue most systems ignore.
05 · Method 05
Search the surrounding context.
What were you working on? What else did you save around the same time? Was it connected to a project, a piece of research, a person?
Context turns a vague memory into a small set. You may not remember the screenshot, but you remember the week it belonged to, and screenshots from one sitting almost always belong to one piece of thinking.
06 · Example
Turn the memory into clues.
“I remember a dark dashboard with orange accents from fintech research.” That sentence looks vague. It contains four usable clues.
What you remember
“I remember a dark dashboard with orange accents from fintech research.”
What you get back
A handful of screenshots from one research week, including the one you meant.
07 · Where Shelf fits
Shelf is built for incomplete memories.
Shelf indexes the text it reads inside your screenshots, a short description of what each one appears to be, when it arrived, and what it was kept alongside. A query can combine those, so an approximate sentence behaves like a search.
Nothing here requires you to have named the file, tagged it, or filed it anywhere.