[myrroddin]

As for finding valid and invalid (turns out I need both, but need to know the difference) this might work:

local valid = true
for w in string.gmatch(text_store, "%d+") do
    if string.gmatch(w, "i:%d+") then
        valid = true
    else
        valid = false
        break -- we only need to find one incorrect itemID. no point in continuing
    end
end