Hi Navyasree
Very generous of Eggy and JJLAPIN to recreate the graphs in vector form.
Unfortunate that the data was lost or unavailable. If by chance these graphs were ever put in any publication, they most likely were put in vector format possibly in a PDF wrapper (most publications want vector and not raster images). If it was ever published, the good news is, the article(s) are likely by download as PDF and from there, the vector graphics can be extracted and then available for reuse.
This happens all the time for thesis and/or technical publications work if graphs from someone else's work (or even you own) and you need to use that in your own publication (of course with credit given if it was someone else's work).
Just another angle to consider if you find yourself in this position again.
John Wheeler