It’s at the bottom of the doc:

echo "Checking for infected AUR packages (${#INFECTED_PKGS[@]} total)..."
echo

found=()
for pkg in "${INFECTED_PKGS[@]}"; do
    if pacman -Qi "$pkg" &>/dev/null; then
        found+=("$pkg")
    fi
done

if [[ ${#found[@]} -eq 0 ]]; then
    echo "Clean: none of the known infected packages are installed."
else
    echo "WARNING: ${#found[@]} infected package(s) found:"
    for pkg in "${found[@]}"; do
        echo "  - $pkg"
    done
fi

Not sure why it uses -Qi instead of -Qm since there’s no point in scanning pacman packages, but I’m no expert