Although I am no ghost whisperer, I did verify the fact that the International Genealogical Index does disappear from the filtered responses in the FamilySearch.org Historical Record Collections. First some history and an explanation of the concerns.
Quoting from the FamilySearch Research Wiki:
The International Genealogical Index (IGI) is a computer file created by The Church of Jesus Christ of Latter-day Saints. It was first published in 1973 and continued to grow through December 2008. It contains several hundred million entries, each recording one event, such as a birth, baptism (christening), marriage, or death.
Information in the IGI came from two sources:
1. Some of the entries in the IGI were indexed by the genealogical community from collections of vital and church records (approx. 460 million names). Indexed records are valuable sources of primary information. Unfortunately, attempts to prevent duplication resulted in the exclusion of some indexed records.
2. Some of the information in the IGI was contributed by members of the Church about their ancestors (approx. 430 million names). The quality of this information varies. Duplicate entries and inconsistent information are common. Always verify contributed entries against sources of primary information.That said, it is also important to understand the limitations of the IGI. Here is a summary, again from the FamilySearch Research Wiki:
The International Genealogical Index is a finding aid. Always check original sources. Entries often do not contain all the information in the original records, such as death dates or names of additional relatives. Sometimes only portions of parish records or other sources were indexed.
Today’s implementation of the International Genealogical Index addresses key deficiencies in the previous implementation. However, it is not able to correct all of them.
1. Previously, the IGI could not be searched by city or parish name, but only by country and one subdivision (such as U.S. state or U.K. county). Users compensated by searching by batch number. While batch number searching is still supported, most users will prefer searching by name instead of number.
2. Previously, indexed entries and community contributed entries were mixed into a single collection. The reliability of the two is different, so users needed to know the source of each result. Users compensated by examining the first digit of the batch number of each result. Batch number charts assisted users in recognizing indexed (“extracted”) entries and user contributed entries. Today, the two types are searched separately, assisting users to distinguish between them.
3. While it grew to contain a tremendous amount of duplication, the IGI was originally envisioned as a file containing just one entry for each birth and each marriage that has ever occurred. When new records were indexed, entries were discarded that duplicated existing IGI entries. To compensate for this limitation, when an entry is not found among indexed entries, search the community contributed entries as well.
4. The original sources for entries in the IGI are not shown. For an indexed entry, look up the film number in the FamilySearch or Family History Library catalog. For a community contributed entry, the contributor may or may not have specified a source. See “Finding the Source of IGI Batch Numbers” for more information.Notwithstanding all that, some people still view the records as valuable. The issues surrounding the IGI accompany the transition of the FamilySearch.org website from the old version to the new version in December 2010. Initially, the IGI was not included in the new website. Finally, with some of the data removed and included in Family Tree, the IGI was returned in its present format with the separation of the Community Contributed IGI and the Community Indexed IGI in two separate files. However, users can select whether to search both files simultaneously or each individually.
The IGI is fairly easy to find. A Google search for "IGI" produces the IGI page on FamilySearch.org and a search in the "Browse All Published Collections" portion of the FamilySearch.org search page will also produce the IGI when you begin typing "international" into the filter. As some commentators to previous posts have indicated if you filter the entire list to a specific country such as England, the reference to the International Genealogical Index disappears. So, this is a problem. But the database itself is available and fully functional.
Just in case you are unable to find the IGI here is the link.