Just checked my spells for my paladin and can no longer find searing smite in the spell list. 

All smites have disappeared actually

Do you have access to the Smite spells via purchase or content sharing?

I've had this happen also. I have a Paladin character which still has Searing Smite on their list. A friend of mine who also has a Paladin (and has access though me sharing content with the campaign) has had Searing Smite disappear from her spell list.

Comparing our two spell lists, she is missing Ceremony, Compelled Duel, Searing Smite, Thunderous Smite and Wrathful Smite. Both Level three characters, mine is Oath of Ancients, hers is Oath of the Crown in case that makes any difference.

Branding Smite is the only paladin "Smite" spell in the free Basic Rules.  In both your case, mstrnugget90, and that of your friend, Spideymark, that the players in question don't "own" the spells from the PHB here on DDB but were not in a campaign with content sharing turned on.  Either the characters left the campaign, or content sharing was turned off by the person who had the Master Tier subscription and had turned it on.

If content sharing still shows as being on in the affected campaign(s), the owner of the Master Tier subscriber should turn it off and back on again.

That was it, somehow content sharing for that campaign had been turned off. Thanks

I have an Oath of Devotion Paladin (4) and I want to know where are the alternate smites (thunderous, wrathful)? Are they not available through the spell list? Are OofD Paladins limited to just Divine Smite?

Sorted. I had to turn content sharing on and off again and re-load the character. Smites are back.