archive_available misses hits

[geotheory]

archive_available() function seems to be missing hits. E.g.

https://web.archive.org/web//https://twitter.com/geotheory/

> archive_available('http://twitter.com/geotheory')
# A tibble: 1 x 5
  url             available closet_url                        timestamp           status
  <chr>           <lgl>     <chr>                             <dttm>              <chr> 
1 http://twitter… TRUE      http://web.archive.org/web/20141… 2014-11-29 00:00:00 200

Am I missing something about the implementation?

[geotheory]

Hmm I just realised that's a positive response - it wasn't earlier. This currently illustrates the issue:

> archive_available('https://twitter.com/geotheory/status/1114823496587251712')
# A tibble: 1 x 5
  url                                             available closest_url timestamp status
  <chr>                                           <lgl>     <lgl>       <lgl>     <chr> 
1 https://twitter.com/geotheory/status/111482349… FALSE     NA          NA        404

Could this be a Wayback server-side issue?