Modifying search settings to not filter adult content did not impact whether the terms begun returning results, regardless of whether the search is set to scan any user, anywhere, and in all languages. Some users reported the words “gay” and “lesbian” were also not returning results, though both of those terms worked in a test by Gizmodo early Sunday afternoon.

In a tweet, LGBTQ advocacy group Human Rights Campaign wrote, “.@TwitterSupport we’re surprised to see some searches for #bisexual and #gay blocked. We urge you to fix—#LGBTQ visibility matters.”

Some users speculated the disappearance of search results was related to automatic filtering of supposedly pornographic content. Others pointed to a November 3rd rules update by the site that was commonly misinterpreted as a move to ban all adult media from the site (Twitter’s policy on adult and sexual services only applies to paid advertisements and was never actually changed, so it’s not clear how it could be relevant).

It’s easy to see why bisexual users are worried. One longstanding concern of the bi community has always been the mistaken beliefs there are only two valid categories of sexual orientation (hetero and same-sex) or that bisexuality is synonymous with promiscuity, and thus that others will seek to erase or stigmatize their identity. So if Twitter was deliberately censoring bisexual content, that’d be a big deal—but it’s not great if the disappearance of the search results was unintentional or the result of some kind of automated censor, either.

“Every bi-activist knows the problems of trying to search for bi-content on the web and some public wifi systems block it altogether, even when it’s nothing to do with sex, because bisexual is seen as a dodgy word in itself,” Bisexual Index campaigner Kate Harrad told the BBC. “This is why Twitter needs to be very sensitive to any filtering that reduces access to bi content, and very aware of the problem of bisexual erasure.”

Update 7:00pm ET: Though Twitter did not respond to Gizmodo’s request for comment, its support account did post late Sunday afternoon saying “We’ve identified an error with search results for certain terms. We apologize for this. We’re working quickly to resolve & will update soon.”

However, searching for the term on the website still returned no results.

It’s still unclear how the “error” occurred in the first place, though the continued persistence of the problem hours after the company acknowledged it suggests a solution at a deeper technical level than simply removing the term from a list. As TechCrunch noted, after Twitter’s seemingly ineffective response to years of widespread harassment on the site, some users have complained the site is still doing a poor job of moderating content.