A sudden Hive spike caused my all swap.hive locked or might be lost forever.

It shouldn't be possible to lose swap tokens because both sides of the transaction get recorded in the same block.

Have you looked through the transactions on HE Explorer?

https://he.dtools.dev/@r1s2g3

NOTE: Last year I "lost" 10 HIVE in a BLURT swap when BLURT collapsed.

I could find all of the pieces of the transactions on Hive-Engine ... the BLURT people kept the coins anyway.