how can you tell if someone blocked you on iMessage

there isn't a notification or anything definite. the signs people go by: your messages stop saying Delivered under the last one, and calls go to voicemail after one ring or none. problem is a phone that's switched off, out of signal or on a Focus mode does exactly the same. so if it's been a day or two it could easily be that. if it's been weeks and they're clearly active elsewhere, well.