come upon vs regain

come upon and regain both are verbs.

Word	Noun	Adjective	Verb	Adverb
come upon	No	No	Yes	No
regain	No	No	Yes	No

As verbs, regain is a hypernym of come upon; that is, regain is a word with a broader meaning than come upon:

come upon: find unexpectedly
regain: come upon after searching; find the location of something that was missed or lost

Other hypernyms of come upon include find.

come upon (verb)	regain (verb)
take possession of	get or find back; recover the use of
find unexpectedly	come upon after searching; find the location of something that was missed or lost