RxJS how to grab first values that is not null from two promises

I'm trying to wrap my head around how RxJS concat works, and how it works with Promises in general.

I have two observables:

currentConfirmation$ emits null

newConfirmation$ emits a new confirmation

Could someone explain why this works:

const finalConfirmation$ = currentConfirmation$.pipe(
    switchMap((conf) => {
      if (!conf) {
        return newConfirmation$
      }

      return of(conf)
    })
  )

But this does not

const finalConfirmation$ = concat(currentConfirmation$, newConfirmation$).pipe(find((conf) => !!conf))

By not works I mean this test passes with the switchMap version and times out with the concat version

test("updateConfirmation should create the confirmation if it doesn't exist", (done) => {
    updateConfirmation({ value: true, symbol: 'LTCUSD', name: 'LTC_TEST_CONFIRMATION_999' }).subscribe((conf) => {
      expect(conf.entityData).toEqual({ value: true, symbol: 'LTCUSD', name: 'LTC_TEST_CONFIRMATION_999' })
      done()
    })
  })

I would also love to know if there is a better approach to accomplishing the above than what I have come up with.

Edit: Here is all the relevant code for the test:

export const confirmationRepository$ = client$.pipe(
  switchMap(async (client) => client.fetchRepository(schema)),
  delayWhen((cr) => from(cr.createIndex())),
  shareReplay(1)
)

export const updateConfirmation = (newData: Partial<Confirmation>) => {
  // TODO: Just don't process the search if we get empty strings
  const currentConfirmation$ = getConfirmation(newData.symbol || ' ', newData.name || ' ')
  const newConfirmation$ = createConfirmation(newData)

  // const finalConfirmation$ = concat(currentConfirmation$, newConfirmation$).pipe(find((conf) => !!conf))
  const finalConfirmation$ = currentConfirmation$.pipe(
    switchMap(async (conf) => {
      if (!conf) {
        return newConfirmation$
      }
      return of(conf)
    }),
    concatAll(),
    combineLatestWith(confirmationRepository$),
    concatMap(async ([conf, confRepo]) => {
      conf.value = !!newData.value
      await confRepo.save(conf)
      return conf
    })
  )

  return finalConfirmation$
}

export const getConfirmation = (symbol: string, name: string) => {
  return confirmationRepository$.pipe(
    switchMap((cr) => cr.search().where('symbol').equals(symbol).and('name').equals(name).first())
  )
}

export const getConfirmations = (symbol: string) => {
  return confirmationRepository$.pipe(switchMap((cr) => cr.search().where('symbol').equals(symbol).returnAll()))
}