URLs submitted in sitemap with rewritten URLs have started to be indexed wrongly

Hello,

I would like to bring to attention an issue I have observed over the past several days (7-10 days, approx.). I run a rather large blog using WP 2.7.1 and I chose a “day and name” permalink structure, something along the lines of https://www.mysite.com/2009/03/18/sample-post/

I use Google sitemaps and the XML Sitemaps plugin to help indexing since I have over 15,000 pages in my site and everything worked well until recently, when I noticed Google decided to index the URLs using the standard post ID parameter and not what was submitted.

To give an example:

This URL was indexed – https://www.adoperationsonline.com/?p=2528 – however, what was submitted through the sitemap was https://www.adoperationsonline.com/2009/01/26/search-engine-strategies-ses-london-conference-expo/ .

I’ve checked and doublechecked: the URLs in my sitemap are carrying the correct day and title structure, yet they end up indexed in their raw form using the post ID parameter.

Has anybody faced something similar, or does anyone have any suggestions on how to fix this issue? Indexing using the post ID is terrible and very reader-unfriendly. Plus, ever since this happened, my indexed pages have taken a serious hit, from 11,300 to under 9,000 currently and the trend is downwards. I’ve changed absolutely nothing in the site settings, so why the sudden indexing going all wrong? I repeat, pages used to be correctly indexed with their friendly URLs until not long ago, when they all became post ID-based.

Is this something you have bumped into and can give some feedback?

Thanks,
Otilia