What to do if he flirts then goes distant for days

Read the gap as information about how much room he has right now, not a verdict on you. He sent something warm and unprompted, which tells you he likes the attention. Then he stopped, which usually means he hasn't decided how much effort this takes. Check whether the flirting came with a question, a suggestion, or a plan. If it did, the silence is more likely a busy week. If it was only compliments and jokes, he's probably keeping things light and low stakes, and you shouldn't raise the stakes for him. Pay attention to whether he ever follows through on anything he suggests. Someone who vanishes after every warm message and never converts it into a time or place is showing you his pattern, and that pattern matters more than any single text.

A good reply does three jobs. First, it accepts the flirt at face value. Let his compliment land with one light line that shows you enjoyed it, so he doesn't have to wonder whether you took it as a joke. Second, it hands him something specific to respond to, such as a detail from earlier in the chat or a small question he can answer in a sentence. Open loops work better than broad questions about how things are going. Third, it leaves the silence unremarked. Don't mention the days he was gone, don't ask why he disappeared, and don't match his distance with your own. Your reply should read like it came from someone with a full week, because that's the impression you want him to notice. Keep it short enough that he can answer in under a minute.

Timing matters as much as wording here. Send your reply at a normal hour, roughly when he usually texts, rather than late at night when a message can read as needy. If he answers within a day, match his pace and steer toward a concrete plan. If he doesn't answer, wait about three days before doing anything else, since people who vanish often come back in that window with a casual message. If you do send a second message, keep it short, light, and tied to something real you both mentioned, like a place or a show. Then stop. Two unanswered messages after a week of silence is a clear enough answer about his available time. Put your attention back on your own plans and see whether he comes to you.