It is not unusual for a newly published page to rank highly at first, then drop or disappear before settling into a more stable position. This happens because Google's systems are still determining how relevant and authoritative the page is compared with other content on the web. As Google gathers more signals and better understands the page, rankings may fluctuate before stabilising.
These fluctuations are a normal part of the indexing and ranking process and do not necessarily indicate a problem with the page or website.