Mad thought here - did you change your mulching and watering regime at all? The poppies do well in much drier conditions than those preferred by raspberries, so you might have been getting an indication of habitat change - as well as a possible antipathy between species.

Perhaps while planting the poppies you also added more mulch which smothered the base of the raspberries. I've read that especially in our climate they can't be too deep.

There are some diseases raspberries can get, so perhaps something was spread to them.

Other ideas needed more water this summer or the raspberries crowded themselves out.

Mine spread like crazy out of the row, so there are always replacements.

You might find some more at the exchange site below. The Green Elephant swap was last Saturday & I shared dozens of them & saw others, so it was a good year for raspberry runners. I dug mine in spring & pulled a few out in fall.

Here is a link that might be useful: Pacific Northwest Garden Exchange