This isn't about never raising a problem you haven't solved. It's about the difference between handing someone a problem and handing them a starting point.
"The vendor is going to miss the deadline" is a fact, not a contribution. Said on its own, it puts the entire burden of figuring out what to do next on whoever you just told, usually your boss, who now has to stop what they're doing and think through a problem they didn't have five minutes ago. Said with even a rough option attached, the same fact becomes something they can actually act on.
This doesn't require you to have the answer. It requires you to have thought about it for five minutes before bringing it to someone else's desk. There's a real difference between "I don't know what to do" and "here's what I'm considering, but I want your read on it", the second one shows you've already done the first pass of thinking, even if you're genuinely unsure of the right call.
"Hey, the vendor just told us they're going to miss the deadline. What do you want to do?"
"The vendor just told us they're going to miss the deadline by about a week. I see two options: push our internal date to match theirs, or bring in a backup vendor for the piece that's blocked, which would cost more but keep us on schedule. I'm leaning toward pushing the date since the backup vendor is untested. What's your read?"
The second version takes maybe two extra minutes to put together, and it completely changes what happens next. Instead of your boss doing the thinking from zero, they're evaluating a judgment call you've already made a first pass at, which is a faster conversation, and one that quietly builds their confidence that you can be handed ambiguous problems without needing to be walked through every step.
One caution worth naming: this isn't permission to sit on a real problem until you've found the perfect solution, or to soften something urgent because you don't yet have an answer ready. If something is time-sensitive or serious, raise it immediately, even with nothing attached, "I don't have a plan yet, but I need to flag this now" is still better than staying quiet while you think. The rule is about habit, not about delaying urgent news to look more prepared.
Over time, this is one of the fastest ways to change how much responsibility gets handed to you. People who consistently show up with a thought-through option, even an imperfect one, get trusted with bigger and more ambiguous problems. People who consistently show up with just the problem tend to get smaller ones.