grep sed and awk to find a specific string inside a very long single line string using regex

( Any example from me will fail cause this is a complex html/java file, so it is impossible to provide such example as asked by Mods)

i want to grep the following string photo-models","title":"Abby%20from%20the%20Philippines.","description":"OLYMPUS%20DIGITAL%20CAMERA"," in the following html file HERE

i tried the following codes as suggested in different stackoverflow topics about (and many variations). However, it prints the whole file and not the specified string.

awk '/_flickrModelRegistry/,/license/' index.html
grep -Poza '_flickrModelRegistry.*license' index.html | head -n1
sed -n '/_flickrModelRegistry/,/license/p'  index.html

so, how i can grep this string inside this file?

UPDATE:

I thought that it was a multiline problem but eventually it is a single-long-line-string problem.