How late did the lost works of Euripides survive?

I notice that the in almost every book on ancient Greek drama, there is a mention that the majority of work is lost.

Example:

*# Lost plays of Aristophanes. He wrote forty plays, eleven of which survive.
. . .

Lost plays of Euripides. He is believed to have written over ninety plays, eighteen of which have survived. Fragments, some substantial, of most other plays also survive.
*

If these plays are lost forever, do we at least know when (if not where) they were lost? About when were the last generations of humans to have had access to these plays (in manuscript)? Was is it the Library of Alexandria they were lost? Or later, in the 4th crusade and its sack of Byzantium?

I realize it is theoretically possible that these lost works still survive somewhere. What is the probability of any of these plays showing up within the next thousand years?

Most ancient manuscripts were never common. There may never have been more than a few dozen written copies of Aristophanes’ plays prior to the invention of modern printing. So there was never a specific generation that lost them - for most people they were always lost.

Look at Tactitus. The reason we have any of his histories is because one single copy happened to survive. All of the thousands of copies we have now are reprints from that one manuscript. That copy was missing about a third of the total so we don’t have those parts.

The works of Cicero were much admired and frequently quoted by other writers in the ancient world, and in some cases they have been pieced back together from these quotations.

Every so often they do find a big depository of ancient manuscripts - I believe the one at IIRC Herculaneum is fairly recently discovered and they’re still looking at it. That doesn’t mean that it has anything “lost” in it, though.