I use many skins on my server for making custom items using plugins and playerheads for decorations too.  A few textures just recently disappeared which I had been using for months beforehand.  Some of which are skins from https://minecraft-heads.com and some of which I made myself using other skin services. 

One of which is this skin texture: 

ewogICJ0aW1lc3RhbXAiIDogMTY0ODE3NDU2MDgxOCwKICAicHJvZmlsZUlkIiA6ICI5MThhMDI5NTU5ZGQ0Y2U2YjE2ZjdhNWQ1M2VmYjQxMiIsCiAgInByb2ZpbGVOYW1lIiA6ICJCZWV2ZWxvcGVyIiwKICAic2lnbmF0dXJlUmVxdWlyZWQiIDogdHJ1ZSwKICAidGV4dHVyZXMiIDogewogICAgIlNLSU4iIDogewogICAgICAidXJsIiA6ICJodHRwOi8vdGV4dHVyZXMubWluZWNyYWZ0Lm5ldC90ZXh0dXJlLzQ2OGMxZmE0YTIxYmE0ZjI3ZGNiMzBhYjNiZmFiMGRjMjJhMWU0ZmNmOWVkMTJjMWQ3YTcwZmViMDdmOGQ3YWUiLAogICAgICAibWV0YWRhdGEiIDogewogICAgICAgICJtb2RlbCIgOiAic2xpbSIKICAgICAgfQogICAgfQogIH0KfQ==

which corresponds to this URL: http://textures.minecraft.net/texture/468c1fa4a21ba4f27dcb30ab3bfab0dc22a1e4fcf9ed12c1d7a70feb07f8d7ae which reports that it is 404 Not Found currently.  Can you please look into this issue?  I do keep a copy of all skins that I use on the minecraft server that I host with the corresponding skin id on my web server.  (Sadly I know that minecraft in like version 1.7 or very long ago disabled the ability to use any other server except Mojang for loading textures for skins.)  It would be hard for me to fix all the instances of this item as many players have them.  Would you be able to restore this and any other missing skins that were maybe accidentally removed within the last week?